power electronics lab manual, dr. b g shivaleelavathi, jssateb

Department of Electronics & Communication Engineering

JSSATE, BENGALURU 1

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JSSATE, BENGALURU 3

JSS ACADEMY OF TECHNICAL EDUCATION

(AFFILIATED TO VTU)

Uttarahalli-Kengeri Main Road, Mylasandra

Bangalore – 560060

DEPARTMENT OF ELECTRONICS &

COMMUNICATION ENGINEERING

POWER ELECTRONICS LAB MANUAL (10ECL78)

(VII SEM)

Dr. B. G. Shivaleelavathi,Professor,

Sunitha L Siraatti, Asst. Prof.,

Sangeetha K. N. Asst. Prof.,

E&C Dept.,

JSSATE, Bangalore.


JSSATE, BENGALURU 4

INDEX

SERIAL

NO.

CONTENTS PAGE

NO. 1 Power Electronics lab syllabus

3

2 Static characteristics of MOSFET and IGBT

4 to 9

3 Static characteristics of SCR, TRAIC and DIAC

10 to 17

4 Controlled HWR and FWR using RC triggering circuit

18 to 25

5 SCR turn off using i) LC circuit ii) Auxiliary

Commutation

26 to 33

6 UJT firing circuit for HWR and FWR circuits

34 to 43

7 Generation of firing signals for thyristors / TRIACs using

digital circuits/microprocessor.

44 to 47

8 AC voltage controller using TRIAC-DIAC combination

48 to 50

9 Single phase Fully Controlled Bridge Converter with R

and R-L loads

51 to 73

10 Voltage (Impulse) commutated chopper both constant

frequency and variable frequency operations

74 to 83

11 Speed control of a separately exited DC motor.

84 to 89

12 Speed control of universal motor.

90 to 91

13 Speed control of stepper motor.

92 to 96

14 Parallel / Series inverter

97 to 105

15 spice-simulator.

16

17 Model questions

106

18 Viva questions

107

19 Bibliography

108


JSSATE, BENGALURU 5

POWER ELECTRONICS LAB

Subject Code: 06ECL78 IA Marks: 25

No. of Practical Hrs/Week: 03 Exam Hours: 03

Total no. of Practical Hrs: 42 Exam Marks: 50

1. Static characteristics of MOSFET and IGBT.

2. Static characteristics of SCR, TRIAC and DIAC.

3. Controlled HWR and FWR using RC triggering circuit

4. SCR turn off using i) LC circuit ii) Auxiliary Commutation

5. UJT firing circuit for HWR and FWR circuits.

6. Generation of firing signals for thyristors/ TRIACs using

digital circuits/microprocessor.

7. AC voltage controller using TRIAC-DIAC combination.

8. Single phase Fully Controlled Bridge Converter with R and R-L loads

9. Voltage (Impulse) commutated chopper both constant frequency and

variable frequency operations.

10. Speed control of a separately exited DC motor.

11. Speed control of universal motor.

12. Speed control of stepper motor.

13. Parallel / Series inverter.


JSSATE, BENGALURU 6

1) STATIC CHARACTERISTICS OF MOSFET AND IGBT

(i) STATIC CHARACTERISTICS OF MOSFET .

AIM: To plot input and transfer characteristics of an MOSFET and to find ON state resistance

and trans conductance.

APPARATUS: 1. 0 – 50V DC Voltmeter

2. 0 – 100V DC Voltmeter

3. 0 – 100mA DC Ammeter

4. Regulated power supply

5. n-channel MOSFET (IRF-840)

6. Resistance (500Ω/5W).

DEVICE SPECIFICATIONS: IRF 840. 1. VDss-Drain to Source Breakdown voltage : 400 Volts.

2. Rds (on)-On state Resistance : 0.55 ohms.

3. ID-continuous drain current-25° C : 10 Amps.

4. ID-continuous drain current-100° C : 6.3 Amps.

5. RJC-Max thermal resistance : 1° C/Watt.

6. PD Max-power dissipation@ 25° C : 125 watts.

CIRCUIT DIAGRAM:

ROCEDURE:

i) Transfer Conductance Characteristics:

Make the connections as shown in the circuit diagram including meters. Initially keep V1 and V2

minimum. Set VDD=VDS1=say 10V. Slowly vary VGG (VGS) and note down ID and VGS readings for

every 1 Volt and enter in the tabular column. The minimum gate voltage VGS that is required for

conduction to start the MOSFET is called Threshold Voltage VGS(Th). The Drain current depends on

magnitude of the Gate Voltage VGS which may vary from 2 to 5 Volts.

Repeat the same for different VDS and draw the graph of VGS V/s ID.


JSSATE, BENGALURU 7

ii) Tabular Column:

VDS1 (Volts) VDS2 (Volts)

VGS (Volts) ID (mA) VGS (Volts) ID (mA)

iii) Drain Characteristics:

Initially set VGG to VGS1=3.5 Volts. Slowly vary V1 and note down ID and VDS. For a particular

value of VGS1 there is a pinch off voltage (Vp) between drain and source.

If VDS is lower than Vp, the device works in the constant resistance region and ID is directly

proportional to VDS. If VDS is more than Vp, constant Id flows from the device and this operating

region is called constant current region.

Repeat the above for different values of VGS and note down VDS Vs ID.

Draw the graph of VDS Vs ID for different values of VGS.

iv) Tabular Column:

VGS1 (Volts) VGS2 (Volts)

VDS (Volts) ID (mA) VDS (Volts) ID (mA)


JSSATE, BENGALURU 8

WAVEFORMS :

Ohmic

ID

mA

0

GS4VActive

GS3V

GS2V

GS1V

GS4V > GS3V > >VGS2 VGS1

DSVvolts Output Characteristics

DI

DSV

Transfer Characteristics

VGS (th)

RESULT: ∆VDS

1. RD = -------------- = ------------------------------ Ω.

∆ID

∆ID

2. Gm = -------------- = ------------------------------ mho.

∆VDS

CONCLUSION: We conclude that MOSFET is a voltage controlled device.


JSSATE, BENGALURU 9

(ii)) STATIC CHARACTERISTICS OF IGBT.

AIM: To plot the characteristics of IGBT.

APPARATUS: 1. 0 – 50V DC Voltmeter

2. 0 – 100V DC Voltmeter

3. 0 – 100mA DC Ammeter

4. Regulated power supply

5. Resistance (500Ω/5W).

6. IGBT (IRGBC-20S)

DEVICE SPECIFICATIONS: IRGBC 20S

1. Vce-Collector to emitter Voltage : 600 Volts.

2. Max Vce(on)-Collector to emitter Voltage : 3.0 Volts.

3. Ic-continuous collector current @ 25° C : 19 Amps.

4. ID-continuous collector current @ 100° C : 10 Amps.

5. Pd max-Maximum power dissipation : 60 Watts.

CIRCUIT DIAGRAM:

PROCEDURE:

i)Transfer Characteristics:

Make the connections as shown in the circuit diagram with meters.

Initially keep V1 and V2 minimum. Set V1=VCE1=say 10V. Slowly vary V2 (VGE) and note down IC

and VGE readings for every 1.0 Volt and enter in the tabular column. The minimum gate voltage

VGE which is required for conduction to start the IGBT is called Threshold Voltage VGE(Th). If VGE

is greater than VGE(Th) only very small leakage current flows from Collector to Emitter. If VGE is

greater than VGE(Th), the Collector current depends on magnitude of the Gate Voltage. VGE varies

from 4 to 8 Volts.


JSSATE, BENGALURU 10

Repeat the same for Vc and draw the graph of VGE V/S IC.

ii)Tabular Column:

VCE1 (Volts) VCE2 (Volts)

VGE (Volts) IC (mA) VGE (Volts) IC (mA)

iii) Collector Characteristics:

Initially set V2 to VGE1=5 Volts. Slowly vary V1 and note down IC and VGE. For a particular value

of VGE1 there is a pinch off voltage (Vp) between Collector and Emitter.

If VGE is lower than Vp, the device works in the constant resistance region and IC is directly

proportional to VGE. If VGE is more than Vp constant IC flows from the device and this operating

region is called constant current region.

Repeat the above for different values of VGE and note down VCE V/S IC.

Draw the graph of VCE V/S IC for different values of VGE.

iv) Tabular Column:

VGE1 (Volts) VGE2 (Volts)

VCE (Volts) IC (mA) VCE (Volts) IC (mA)



WAVEFORMS:

COLLECTOR CHARACTERISTICS

TRANSFER CHARACTERISTICS

RESULT: ∆VCE

1. RON = -------------- = ------------------------------ Ω.

∆IC

2. VGSTh = ------------------------------ Volts

CONCLUSION:

We conclude that IGBT is a voltage controlled device.



2) STATIC CHARACTERISTIC OF SCR, TRIAC & DIAC

(i) STATIC CHARACTERISTIC OF SCR

AIM: To plot the characteristics of an SCR and to find the forward resistance, holding current

and latching current.

APPARATUS: 1) 0 – 50V DC Voltmeter (Digital Multimeter)

2) 0 – 500mA DC Ammeter

3) 0 – 25mA DC Ammeter

4)Resistor (1kΩ/5w)

5)Regulated power supply

6)SCR (TYN616)

7)Rheostat

DEVICE SPECIFICATIONS: TYN 616

1. Vrrm : 600V.

2. It(rms) : 16 A.

3. It(av) : 10 A.

4. It(sm) : 160 A.

5. It : 128 A/µs.

6. di/dt : 100 A/µs.

7. Igt : 25 mA.

8. Vgt : 1.5 V.

9. IH : 40 mA.

10. IL : 70 mA.

11. tq : 70µs.

12. dv/dt : 500 V/µs.

CIRCUIT DIAGRAM:

Note: R1 is a rheostat of 1kΩ (/2amp).



PROCEDURE:

i). V-I Characteristics: Make the connections as given in the circuit diagram. Now switch ON the mains supply to the unit

and initially keep VGG & VAA at minimum. Set load potentiometer R1 in the minimum position.

Adjust Ig to Ig1 say (2 to10) mA by varying VGG. Slowly vary VAA and note down VAK and IA

readings for every 5 volts and enter the readings in the tabular column. Further vary VAA till SCR

conducts, this can be noticed by sudden drop of VAK and rise of IA readings. Note down this

reading and tabulate. Vary VAA further and note down IA and VAK readings. Draw the graph of VAK

V/S IA.

Repeat the same for Ig = Ig2/Ig3 mA and draw the graph.

Tabular Column:

MODE 1, IG1=

VAA (volts) V AK2 (volts) I AK (mA)

To find latching current: Apply about 20V between anode and cathode by varying VA. Keep the load rheostat R1 at minimum

position. The device must be in the OFF state with gate open. Gradually increase Gate voltage- VGG

till the device turns ON. This is the minimum gate current (Igmin) required to turn ON the device.

Adjust the gate voltage to a slightly higher value. The gate voltage should be kept constant in this

experiment. Now turn OFF the gate voltage. If the anode current is greater than the latching current

of the device, the device stays ON even after the gate switch is opened. Otherwise the device goes

into blocking mode as soon as the gate switch is opened. Note this anode current as the latching

current. Obtain more accurate value of the latching current by taking small steps of IA near the

latching current value.

Increase the anode current from the latching current level by VAA. Open the gate switch

permanently. The thyristor must be fully ON. Now start reducing the anode current gradually by

adjusting (increasing) R1. If the thyristor does not turns OFF even after the R1 at maximum

position, then reduce VAA. Observe when the device goes to blocking mode. Observe that for one

setting of R1 or VAA the anode current suddenly drops to zero. The anode current through the

device at this instant is the holding current of the device. Repeat the steps again to accurately get

the IH. Normally IH<IL.

MODE 2, IG2=

V AA (volts) V AK (volts) I AK (mA)



WAVEFORMS:

RESULT: 1. The break over voltages : Vb1 = -------------- ; Ig1

: Vb2 = --------------- ; Ig2

Latching Current (IL)= ------------------------------------ amps

Holding Current(IH) = ------------------------------------- amps

∆ VAK

Forward Resistance Rf = ------------;

∆ IA

Rf = ------------------------------ Ω

CONCLUSION : We conclude from the experiment that as the gate current increases the break over voltage

decreases.



(ii) STATIC CHARACTERISTIC OF TRIAC.

AIM: To plot the characteristics of TRIAC.

APPARATUS:

1) 0 – 50V DC Voltmeter (Digital Multimeter)

2) 0 – 500mA Ammeter

3) 0 – 25mA Ammeter

4) Regulated power supply

5) Resistor (1kΩ/5w)

6) TRIAC(BT136-600)

7) Rheostat

DEVICE SPECIFICATIONS: BT136-600. 1. Vdrm : 600V.

2. Itrms : 4 A.

3. Itsm : 50 A.

4. It : 12.5 A.

5. di/dt : 10 A/µs.

6. Igt : 15 mA.

7. Vgt : 1.5 V.

8. IH : 13 mA.

9. IL : 50 mA.

10. dv/dt : 10 V/µs.

CIRCUIT DIAGRAM:



PROCEDURE:

i) V-I Characteristics: Make the connections as given in the circuit diagram including meters. Now switch ON the mains

supply to the unit and initially keep VTT & VGG at minimum. Set load rheostat R1 in the minimum

position. Adjust Ig-Ig1 say 10 mA by varying VGG. Slowly vary VAA and note down VT2T1 and IL

readings for every 5 Volts and enter the readings in the tabular column. Further vary VAA till

TRIAC conducts, this can be noticed by sudden drop of VT2T1 and rise of IL readings. Note down

this reading and tabulate. Vary VAA further and note down IL and VT2T1 readings. Draw the graph of

VT2T1 V/S IL. Repeat the same for Ig = Ig2/Ig3 and draw the graph.

To find latching current: Apply about 20V between MT1 and MT2 by varying VAA. Keep the load rheostat R1 at minimum

position. The device must be in the OFF state with gate open. Gradually increase Gate Voltage VGG

till the device turns ON. This is the minimum gate current (Igmin) required to turn ON the device.

Adjust the gate Voltage to a slightly higher value. The gate Voltage should be kept constant in this

experiment. By varying VAA, gradually decrease anode current IL in steps. Open and close the Gate

voltage VGG switch after each step. If the load current is greater than the latching current of the

device, the device stays ON even after the gate switch is opened otherwise the device goes into

blocking mode as soon as the gate switch is opened. Note the latching current. Obtain more

accurate value of the latching current by taking small steps of IL near the latching current value.

Increase the Load current from the latching current level by load pot R1 or V1. Open the gate switch

permanently. The Triac must be fully ON. Now start reducing the anode current gradually by

adjusting R1. If the Triac does not turn OFF even after the R1 at maximum position, then reduce V1.

Observe when the device goes to blocking mode. The load current through the device at this instant

is the holding current of the device. Repeat the steps again to accurately get the IH. Normally IH<IL.

MODES

Modes MT2 MT1 G

Mode1 + - +

Mode2 + - -

M0de3 - + +

Mode4 - + -

Tabular Columns:

MODE 1, IG1=

V TT (volts) V T1T2 (volts) I T1T2 (mA)

MODE 2, IG2=




MODE 3, IG3=


WAVEFORMS:

V-I characteristics

RESULT:

CONCLUSION: We conclude that the sensitivity of the mode depends on minimum gate current required to turn on

the TRIAC. We found that mode1 is most sensitive where as mode 3 is least sensitive.

MODE 4, IG4=




(iii) STATIC CHARACTERISTICS OF DIAC

AIM: To plot the characteristics of DIAC.

APPARATUS:

1) 0-60V DC Voltmeter

2) 0-250mA DC Ammeter

3) Resistor (1kΩ/5w)

4) Regulated power supply

5) DIAC (DB-3)

6) Rheostat

DEVICESPECFICATIONS: DB-3.

Breakdown Voltage: 32V±10%

Power: 0.5 Watts.

CIRCUIT DIAGRAM:

PROCEDURE:

Make the connections as given in the circuit diagram. Keep R2 at maximum resistance position and

do not change this throughout the experiment. Since the device is only a switching device and its

power rating is only 0.5 watts. Keep V1 potentiometer also at minimum position.

Next switch ON the unit and V1 power supply. Vary V1 in steps of 5V and note down the

corresponding Ammeter reading. Vary in steps of 5V up to 25 Volts. After that vary in steps of 1V.

At a particular value of voltage the device conducts. This can be noticed by the sudden increase of

ammeter reading. This is the device breakdown voltage. Vary V1 further and note down the

corresponding V/I readings in the tabular column.



Tabular Columns:

FORWARD CHARACTERSTICS


WAVEFORMS:

RESULT :

VFBO = --------------- (V)

VRBO = --------------- (V)

CONLUSION :

We conclude that DIAC is a bi-directional device.

REVERSE CHARACTERSTICS




3) CONTROLLED HWR AND FWR USING RC TRIGGERING CIRCUIT

(i)RC FIRING CIRCUIT – HALF WAVE RECTIFIER.

AIM: To study Resistance-Capacitance triggering of SCR in half wave mode.

APPARATUS: Step down transformer (230–30V) , Load resistance (100Ω rheostat), Resistance (10KΩ

potentiometer, +100Ω/1W), Power Diodes (IN 4007), SCR (TYN616), CRO.


1. Vrrm : 600V.

2. It(rms) : 16 A.

3. It(av) : 10 A. Ω

4. It(sm) : 160 A.

5. It : 128 A/µs.

6. di/dt : 100 A/µs.

7. Igt : 25 mA.

8. Vgt : 1.5 V.

9. IH : 40 mA.

10. IL : 70 mA.

11. tq : 70µs.

12. dv/dt : 500 V/µs.

CIRCUIT DIAGRAM :



DESIGN:

It can be shown empirically that

RC ≥ 1.3T/2 ≈ 4/ω :

T = 1/f

f = 50Hz

R= R1 + R2

Vc = Vgt + Vd ;

where Vc is capacitor voltage , Vd is diode voltage drop.

At the instant of firing , Vc is assumed to be constant, the current Igt must be supplied by voltage

source through R, D2 and the gate cathode voltage.

Therefore maximum value of R is given by :

R= R1 + R2 ≤ (V- Vgt - Vd ) / Igt ;

Approximate values of R & C can be obtained from the above equations.

EXAMPLE :

RC = (4×π×50) / 2

Let Vgt = 1.5 V, Vd = 0.7 V

Then Vc = 1.5 + 0.7 = 2.2 V

Let Igt(max) = 10mA

R = R1 + R2 ≤ (V- Vgt - Vd ) / Igt ;

R ≤ (32 -1.5 - 0.7) / 10mA

≤ 2.97 KΩ;

&

RC ≥ 1.3T/2 ≈ 4/ω

C ≥ 1.3T/2 ≈ 4/ωR

= 1.3/(2 × 50 × 2.97 × 10-3

)

= 1.01× 10-6

F

Let C = 1µF, then

Let R2 = 100Ω/1W.

PROCEDURE:

i) R- Triggering

Make the connections as given in the connection diagram above. Connect a Rheostat of 100

ohms/1.7A between the load points. Vary the control potentiometer (R1) and observe the voltage

waveforms across load, SCR and at different points of the circuit.

We can vary the firing angle from 0° to 90° only in R triggering (you may have to disconnect the

capacitor to realize R triggering alone). In this triggering the synchronized firing angle can be

obtained easily and economically in the positive half cycle of the supply. But there is a draw back

that the firing angle can be controlled at the most at 90°, since the gate current is in phase with the

applied voltage. A resistor R2 is connected in series with the control potentiometer, so that the gate

current does not cross the maximum possible value Igmax



Draw the waveform across the load and device for different values of firing angles.

ii) RC Triggering

Connect capacitor C to the R triggering circuit to realize RC triggering. Repeat the above

procedure and draw the waveform across the load and device for different values of firing angles.

Note here the firing can varied from 0° to (~)180°.

TABULAR COLUMN:

Firing angle

(degrees)

Theoretical Practical

α = sin-1

(Vn/Vp) 0

Vodc (Volts) Vodc (Volts)

Formula Used : Vodc (theoretical) = Vm × (1+ cos α) / (2 π) Note: Show sample calculations for design and Vodc (theoretical)



WAVEFORMS :

Waveforms across Vc , Vload , Vscr , w.r.t to source



RESULT :

CONCLUSION : The average O/P voltage can be varied by varying the firing angle (α).

(ii)RC FIRING CIRCUIT – FULL WAVE.

AIM: To study Resistance- capacitance triggering of SCR in full wave mode.


potentiometer, 100Ω), Power Diodes (IN 4007), SCR (TYN616),CRO.


1. Vrrm : 600V.

2. It(rms) : 16 A.

3. It(av) : 10 A.

4. It(sm) : 160 A.

5. It : 128 A/µs.

6. di/dt : 100 A/µs.

7. Igt : 25 mA.

8. Vgt : 1.5 V.

9. IH : 40 mA.

10. IL : 70 mA.

11. tq : 70µs.

12. dv/dt : 500 V/µs.

CIRCUIT DIAGRAM : RC FIRING CIRCUIT – FULL WAVE.

NOTE : A simple RC trigger circuit giving full-wave output voltage. Diodes D1 – D4 form a full-wave

bridge rectifier. Diode Bridge: In this circuit, the initial voltage from which the capacitor C charges

is almost zero. The capacitor C is set to this low positive voltage(upper plate positive) by the



clamping action of SCR gate. When capacitor charges to a voltage equal to Vgt SCR triggers and

rectified voltage Vd appears across load as Vo.

DEISGN :

Same as for Half wave triggering

PROCEDURE:

Make the connections as shown in the circuit diagram above. Switch ON the unit. By varying the

potentiometer on the front panel, note down the voltage waveforms across the load( 100 Ohms/2A

rheostat) and also across SCR and capacitor. Infer on the control obtained with and without

capacitor connected to the circuit. Draw the waveforms across load, SCR and across capacitor.

TABULAR COLUMN:

Firing angle Theoretical Practical

(α)=sin-1

(Vn/Vp)0

Vodc (Volts) Vodc (Volts)

FORMULA USED :

Vodc (theoretical) = Vm ×(1+ cos α)/( π) Note :Show the sample calculations for design and Vodc (theoretical)



WAVEFORMS :



RESULT :

CONCLUSION :

We conclude that the average voltage in FW mode is greater than HW mode. The average O/P

voltage can be varied by varying the firing angle (α).

4) SCR TURN – OFF CIRCUITS USING

(a) LC CIRCUIT (b) AUXILIARY COMMUTATION

AIM: To rig up various turn off circuits for SCR by auxiliary commutation class D commutation.

APPARATUS: Forced commutation study unit, DC power supply (0-30V/2A for Class E Commutation only),

Rheostats (50 ohms / 2A) – 2Nos, CRO, Probes and connecting wires.

DESCRIPTION :

FORCED COMMUTATION STUDY UNIT This unit consists of two parts – (i) Power Circuit and (ii) Firing Circuit sufficient to study (a) Class

A Commutation – Self Commutation by load resonance. (b) Class B Commutation – Self

Commutation by LC circuit. (c) Class C Commutation – Complimentary SCR commutation. (d)

Class D Commutation – Auxiliary SCR commutation. (e) Class E Commutation – with an external

source of pulse for commutation.

POWER CIRCUIT:

This part consists of the following components to build different commutation circuits with

different values of commutation components.

a) 2 SCRs. b) a diode. c) 2 different values of commutation capacitors to get different value of

commutation capacitance by individual, series and parallel connections and d) a commutation

inductor with tappings at different points and a transistor for class E commutation. An unregulated

DC power supply of 24 Volts @ 2Amps is provided to use as DC input for commutation circuits.

FIRING CIRCUIT: This part generates triggering pulses to fire two SCRs connected in different forced commutation

circuits. The frequency and duty cycle can be varied using respective potentiometers.



FRONT PANEL DIAGRAM:

FORCED COMMUTATION STUDY UNIT - FCU

U

POWER

TRIG - OUTPUT

CAT

T2

GATE

1T

OFF

ON

+

ON

E

S

FIRING CIRCUIT

FREQUENCY

MIN MAX

+

F

-

DUTY CYCLE

MIN MAX

C1 C2

T2

1LO L2 L3

T1

DPOWER CIRCUIT

C

B

RT

E

FRONT PANEL DETAILS:

1.Power : Power ON / OFF switch to the unit with built in indicator.

2.Frequency : Potentiometer to vary the frequency of commutation from 30Hz to

250Hz approximately.

3.Duty Cycle : Potentiometer to vary the duty cycle from 10% to 90%

approximately.

4.Trigger Output ON / OFF : On / Off switch for mains pulse T1

5. Gate / Cathode : Positive and negative points of trigger outputs to connect to gate and

cathode of SCRs.

6.T1 : Trigger output for SCR T1 – 200 µs pulse.

7.T2 : Trigger output for SCR T2 – 200 µs pulse.

8.Volts dc IN : 24V @ 2A unregulated DC supply is available at these terminals for DC

Source for the commutation power circuit.

9. ON : ON / OFF switch for DC supply.

10.Fuse : 2Amps glass fuse for DC power supply protection.

11. + : DC power supply point after switch and fuse.

12.D : Free wheeling diode – BYQ 28 – 200.

13.T1 & T2 : SCRs – TYN 612.

14.Tr : Transistor – TIP 122.

15. Commutation Inductance

L1 : 250µH

L2 : 500µH

L3 : 1µH @ 2A

16. Commutation Capacitance

C1 : 6.8µF / 100V

C2 : 10.0 µF / 100V



BACK PANEL DETAILS:

Main socket with built in fuse holder. The fuse holder has a spare fuse along with the fuse

in the circuit. If the fuse blows remove the blown fuse and replace with the spare fuse. Fuse – 1A

fast blow glass fuse.

DESIGN OF LC COMMUTATION CIRCUIT :

TON = π[LC]1/2

Let TON = 2 msec , C = 6.8 µF.

Then 2 x 10-3

= π [L x 6.8 x 10-6

]1/2

L = 590 H

PROCEDURE:

Switch on the mains to unit and observe the trigger outputs by varying frequency and duty cycle

potentiometer and make sure that the pulse output are proper before connecting to the power

circuit. Check the DC power supply between the DC Input points.

Check all the devices. Check the resistance between the Gate and Cathode of SCR’s. Check the

resistance between anode and cathode. Check the diode and its polarity. Check the transistor and its

polarity. Check the fuse in series with the DC input. Make sure that all the components are good

and firing pulse is correct before you start any commutation experiments.

(a)CLASS – A COMMUTATION: (SELF COMMUTATION BY RESONATING LOAD -LC)

The current reversing property of the load will force the device commutation. L,C and R values are

chosen such that the circuit is under damped.

Since the commutation elements carry load current on a continuous basis, these ratings are

generally high. For low frequency operation large value of L & C is required.

CIRCUIT DIAGRAM: CLASS–A COMMUTATION: (SELF COMMUTATION BY

RESONATING LOAD -LC)

PROCEDURE:

Make the interconnections in the power circuit as shown in the circuit diagram.

Connect trigger output T1 to gate and cathode of SCR T1. Switch on the DC Supply to the power

circuit and observe the voltage waveform across load by varying the frequency Potentiometer. Duty

cycle Potentiometer is of no use in this experiment.

Repeat the same for different values of L, C and R.



TABULAR COLUMN :

WHEN L = L1 AND C= C1

R (Ω) Ton ( msec) Tc ( msec)

WHEN L = L1 AND R= R1

C (µF) Ton ( msec) Tc ( msec)

WHEN R= R1 AND C= C1

L Ton ( msec) Tc ( msec)



WAVEFORMS: T r i g g e r o u t p u t s :

T 1

T 2

Voltage across the gating pulse, Thyristor, voltge across capacitor, voltage across resistor

RESULT :

CONCLUSION : We conclude that the SCRs can be commutated by using LC circuit also.



CLASS – B COMMUTATION: (SELF COMMUTATION BY AN LC CIRCUIT) In this type of commutation, reverse voltage is applied to the thyristor by the over swinging of an

under damped LC circuit connected across the Thyristor.

Capacitor charges up to the supply voltage before the trigger pulse is applied to the gate. When the

thyristor is triggered, two currents flow, a load current through the external circuit and a pulse of

current through LC circuit and thyristor in opposite direction. This resonant current tends to turn

off the thyristor.

CIRCUIT DIAGRAM: CLASS – B COMMUTATION:(SELF COMMUTATION CIRCUIT)

PROCEDURE:

Make the interconnections in the power circuit as shown in the circuit diagram.

Connect trigger output T1 to gate and cathode of SCR T1. Switch on the DC Supply to the power

circuit and observe the voltage waveform across load by varying the frequency Potentiometer. Duty

cycle Potentiometer is of no use in this experiment.

Repeat the same for different values of L,C and R

WAVEFORMS:

O U T P U T A C R O S S " R "

o n ly f r e q u e n c y v a r i a t io n i s p o s ib l e

RESULT :

CONCLUSION : Thus the SCR’s are commutated by LC circuit for class A and class B LC commutation circuits.



(ii) AUXILIARY VOLTAGE COMMUTATION: (Circuit same as Jones chopper)

PROCEDURE: Make the connections as given in the circuit diagram. Connect T1 and T2 gate pulse from the

firing circuit to the corresponding SCR’s in the power circuit. Initially keep the trigger ON/OFF at

OFF position to initially charge the capacitor, this can be observed by connecting CRO across the

Capacitor. Now switch ON the trigger O/P switch and observe the voltage wave forms at different

frequencies of chopping and also at different duty cycles.

Repeat the experiment for different values of load resistance, commutation inductance and

capacitance. Compare the results with theoretical results.

PARAMETERS AND OBSERVATIONS: 1. Voltage wave form across capacitor.

2. Output voltage waveforms (across the load)

3. Output current waveforms (Through the shunt)

4. Voltage waveforms across Thyristors.

5. Study of variation of voltage and current waveforms with the variation of duty cycle

and frequency.

6. Study of effect of free wheeling diode in case of inductive loads.



5) UJT FIRUNG CIRCUIT(ACVC, HWR & FWR)

(i)UJT FIRING CIRCUIT – TWO SCRS(ACVC)

AIM: To fire two SCR using UJT firing circuit.


potentiometer, 3.3KΩ, 100Ω, 220 Ω, 500V/5W), Power Diodes (IN 4007), Zener diode ,SCR

(TYN616),Pulse transformer, CRO.


1. Vrrm : 600V.

2. It(rms) : 16 A.

3. It(av) : 10 A.

4. It(sm) : 160 A.

5. It : 128 A/µs.

6. di/dt : 100 A/µs.

7. Igt : 25 mA.

8. Vgt : 1.5 V.

9. IH : 40 mA.

10. IL : 70 mA.



11. tq : 70µs.

12. dv/dt : 500 V/µs.

CIRCUIT DIAGRAM :

DESIGN : Let VBB =20V; VD = 0.7V;

Vc = VBB (1- e-t/RC

)

Vp = η VBB + VD ; (η = 0.65)

Since Vc = Vp of UJT

ηVz (1- e-T/RC

)

Therefore T = RC ln [1/(1-n)]

T = time period of output pulse .

The firing angle α is given by

α = ωT = ωRC ln [1/(1-n)]

ω = angular frequency.

Vodc(th) = Vm (1+ cosα) /2π The leakage current drop across R1 should be small that when UJT is OFF it should not trigger i.e.,

VBB =I1eakage(RBB + R1+R2 )< SCR trigger voltage.

and R2 = 104

/( η VBB )

width of triggering pulse is R1 C = T2

When voltage drop across C reaches Vp voltage across R is VBB – Vp .

Therefore Rmax = (VBB - Vp ) / Ip

Rmin = (VBB - Vv )/Iv

PROCEDURE:

2.1. Firing of SCR using UJT.



Switch on the mains supply observe and note down the wave forms at the different points in the

circuit and also the trigger O/Ps – T1, & T1’.

Now, make the connections as given in the circuit diagram above ,using AC source, UJT

relaxation oscillator, SCR and suitable load(100ohms /2A rheostat). Switch ON the mains supply,

observe and note down the output waveforms across load and SCR. Draw the wave forms at

different firing angles as 120, 90 & 60 degrees. In the UJT firing circuit the firing angle can be

carried from 150° – 30° approximately.

This is one of the simplest methods of SCR triggering. We can also fire SCR’s in the different

power circuits as described earlier.

2.2. UJT Relaxation Oscillator: To study oscillator using UJT, short Cf to the diode bridge rectifier to get filtered DC output. Now

we will get the equidistant pulses at the O/P of pulse transformer. The frequency of the pulse can be

varied by varying the potentiometer RC. Observe and note down the waveforms at different points

in the circuit.

TABULAR COLUMN:

Firing angle Practical Theoretical

(α)=sin-1

(Vn/Vp) Vorms (Volts) Vorms (Volts)

FORMULA USED : Virms = Vm /√2

Vorms (theoretical) = Virms ×[( π- α)/(2 π) + (sin2α/2 π)]1/2

WAVEFORMS :



waveforms across rectifier (Vodc),zener (Vz), capacitor (Vc), resistor (Vr2), load(VL) ,SCR

(Vscr) with respect to source for α = 90 degrees.

RESULT :

CONCLUSION :



We conclude that the pulses obtained from UJT can be used to fire two SCRs also with the help of

a pulse transformer.

(ii)SYNCHRONIZED UJT FIRING CIRCUIT FOR HWR AND FWR TRIGGERING.

UJT FIRING CIRCUIT – HALF WAVE

AIM: To fire SCR for Half Wave using UJT firing circuit.



APPARATUS:

Step down transformer (230–30V) , Load resistance (100Ω rheostat), Resistance (50KΩ


(TYN616),Pulse transformer, CRO.


1. Vrrm : 600V.

2. It(rms) : 16 A.

3. It(av) : 10 A.

4. It(sm) : 160 A.

5. It : 128 A/µs.

6. di/dt : 100 A/µs.

7. Igt : 25 mA.

8. Vgt : 1.5 V.

9. IH : 40 mA.

10. IL : 70 mA.

11. tq : 70µs.

12. dv/dt : 500 V/µs.

CIRCUIT DIAGRAM :

DESIGN:

Vc = VBB (1- e

-t/RC )



Vp = η VBB + VD ; (η = 0.65)


ηVz (1- e-T/RC

)




α = ωT = ωRC ln [1/(1-n)]




and R2 = 104

/( η VBB )





PROCEDURE:

1.1 . Firing of SCR using UJT.

Switch on the mains supply observe and note down the wave forms at the different points in the

circuit and also the trigger O/Ps – T1, & T1’. Make sure that the pulse transformer O/P T1 & T1’ are

proper and synchronized.

Now, make the connections as given in the connection diagram above ,using AC source, UJT










in the circuit.

TABULAR COLUMN:


(α)=sin-1

(Vn/Vp) Vodc (Volts) Vorms (Volts) Vodc

(Volts)

Vorms

(Volts)

Formula Used :

Vodc (theoretical) = Vm ×(1+ cos α)/(2 π) WAVEFORMS :




(Vscr) with respect to source for α < 90 degrees.

RESULT :

CONCLUSION :

We conclude that the pulses obtained from UJT can be used to fire SCR.

(iii)UJT FIRING CIRCUIT – FULL WAVE

AIM: To fire SCR for Full Wave using UJT firing circuit.





(TYN616),CRO.


1. Vrrm : 600V.

2. It(rms) : 16 A.

3. It(av) : 10 A.

4. It(sm) : 160 A.

5. It : 128 A/µs.

6. di/dt : 100 A/µs.

7. Igt : 25 mA.

8. Vgt : 1.5 V.

9. IH : 40 mA.

10. IL : 70 mA.

11. tq : 70µs.

12. dv/dt : 500 V/µs.

CIRCUIT DIAGRAM :

DESIGN : Vc = VBB (1- e

-t/RC )

Vp = η VBB + VD ; (η = 0.65)




ηVz (1- e-T/RC

)




α = ωT = ωRC ln [1/(1-n)]




and R2 = 104

/( η VBB )





PROCEDURE:

2.1. Firing of SCR using UJT. Switch on the mains supply observe and note down the wave forms at the different points in the

circuit and also the trigger O/Ps – T1, & T1’.

Now, make the connections as given in the circuit diagram above ,using AC source, UJT










in the circuit.

TABULAR COLUMN:


(α)=sin-1

(Vn/Vp) Vodc (Volts) Vorms (Volts) Vodc

(Volts)

Vorms

(Volts)

FORMULA USED : Vodc (theoretical) = Vm ×(1+ cos α)/( π) WAVEFORMS :




(Vscr) with respect to source for α = 90 degrees.

RESULT :

CONCLUSION : We conclude that the pulses obtained from UJT can be used to fire SCR

6) GENERATION OF FIRING SIGNALS USING DIGITAL FIRING CIRCUIT



AIM :To control firing angle /duty cycle using digital triggering.

APPARATUS: Digital firing circuit, SCR’s( Single or any combination) loads, C.R.O, Probes etc.,

DIGITAL FIRING CIRCUIT:

This firing circuit generates isolated trigger pulses for the phase converter, Triac and DC

Chopper Power Circuits. The firing angle can be varied from 0-180° in steps of one degree and

duty cycle can be varied from 0- 100% in steps of 1% using a thumb wheel switch. The firing

scheme is based on ZCD, fixed frequency line synchronized clock generator, up/down counter, flip

flop and pulse Transformer isolation method.


DIGITAL FIRING CIRCUIT - DFC

Z C D

GENERATOR

CLOCKCOUNTER

LOGIC

CIRCUIT

A CGND

AC Ref

180°

100%

F.A. / D.Cy

Fc

Oscillator

TP

NT

R

TRANSFORMER

PLUSETM

ON

OFF

GND

TRIGGER O/PS

T1

T2 2T '

T '1

MAINS

ISOLATION

1

2

INPUT

FRONT PANEL DETAILS: 1) MAIN : Power ON/OFF switch to the unit with built-in indicator.

2) AC Ref : 10V AC reference input for synchronization.

3) GND : Ground point of the unit to observe the waveforms.

4) A : ZCD output.

5) C : Reset output for resetting the counter.

6) F.A/D.CY : Thumb wheel switch to set the firing angle from 0 to 1800 and Duty cycle

from 0 to 100%

7)1800

/ 100% : Switch to select 1800 (1ph converter) or 100% (chopper) mode

8)Fc Oscillator : Carrier frequency generator-5KHz.

9)R : 10 K ohms potentiometer to vary the no. of pulses from the clock

generator

10) Clock generator : A stable oscillator to generate clock input to the counter (180



pulses or 100 pulses) 3 stage.

11) Counter : 4bit up/down programmable counter.

12) Logic Circuit : Logic and modulator circuit to get TP,TN for 1ph converter and

TM, TA or chopper experiments.

Tp : Train of pulses for +ve cycle

TN : Train of pulses for –ve cycle.

TM : Pulse of 200µ sec for main SCR.

TA : Pulse of 200µ sec for auxiliary SCR.

13) TM ON

OFF : ON/OFF switch for main SCR14) Pulse Transformer

Isolation : Pulse transformer based isolation circuit with amplifier to isolate the Logic

circuit from the power circuit.

15) INPUT 1 and 2 : Input terminals to connect logic inputs.

16) Trigger O/Ps : Pulse Transformer isolated Trigger O/Ps –to

be connected to gate and cathode of SCRs.

T1 and T11: Identical and isolated O/Ps for input-1,T2 and T2

1: Identical and

isolated O/Ps for input-2

BLOCK DIAGRAM:

Digital Frequency N - bit Flip - FlopLogic ckt. + ModulatorCounter (F / F)

+

Driver Stage

ZCD

Carrier Frequency

Oscillator

(~ 5 kHz)

Oscillator

Preset

('N' no. of counting bits)

CLK max

min S

A A

B

B

T TFc

T

T

R ResetLoadReset

CSync.

Signal (~ 8V)

Supply

DC 5V

A

¯

En

DIGITAL FIRING CIRCUIT

A

P

N

AM



PROCEDURE: - Switch ON the mains supply to the unit. Observe AC reference signal and

compare it with ZCD O/P A and reset output C. Observe the carrier frequency oscillator o/p-5khz.

Now set the 1800

(Converter) mode. Observe the counter O/P keep the firing angle at 179°.

Adjust the potentiometer R in such a way that a very small pulse at the counter O/P is obtained.

Now vary the firing angle from 1800 to 0

0 step by step and observe the variation in trigger O/Ps TP

and TN. Connect TP and TN to 1 and 2 input of pulse Transformer isolation circuit and we will get

the pulse Transformer isolated and amplified outputs at T1 & T11 and T2 & T2

1 respectively.

Connect these Trigger O/Ps to gate and cathode of SCRs for different power circuits as given in the

table. Now set the 1800-100% switch to 100% mode (chopper) keep the duty cycle at 99%. Adjust

the potentiometer ‘R’in such a way that a very small pulse output is obtained. Now vary the duty

cycle in steps from 99% to 1% and observe the counter O/P and also observe the time variation

between main pulse TM and auxiliary pulse-TA. Connect TM and TA to input 1 and 2 of pulse

transfer isolation.

TABLE

Experiment TRIGGER I/P’S TRIGGER O/P’S

TP TN TM TA T1 T11 T2 T2

1

1)Single Ph-half wave converter.

2)1-ph-full wave converter.

3)1-ph-half controlled bridge

4)1-ph-Fully controlled bridge

5)1-ph.AC phase control

6)Triac (short T1-T2 +ve –ve)

7)Complimentary commutation

8)Auxiliary commutation

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

Table shows the useful Trigger inputs and Trigger outputs for different experiments.



WAVE FORMS:

0

1

P

e

2Wt

3

0

A

F

A

F1

0

A

Wt

Wt

A

0

Wt

Wt

Wt

0

C

Down

0

Counting

16th pulse ofI f

N pulse

A

0

Wta 2 3

0

B

Wt

0

B

Wt

Wt

Wt

0

C

0

G1

a 2 3

2

0

G

a+ 2

G = A,B, I1 c

G = A,B, I2 1

RESULT:

CONCLUSION :

7) AC VOLTAGE CONTROLLER USING TRIAC – DIAC COMBINATION



AIM : To fire TRIAC using DIAC.

APPRATUS REQUIRED :

Dimmer stat ,Isolator, Lamp Load, Resistor ,Potentiometer ,Capacitor,

DIAC( DB -3) ,TRIAC (BT-136), Power scope.

DEVICE SPECIFICATIONS: BT136-600. 1. Vdrm : 600V.

2. Itrms : 4 A.

3. Itsm : 50 A.

4. It : 12.5 A.

5. di/dt : 10 A/µs.

6. Igt : 15 mA.

7. Vgt : 1.5 V.

8. IH : 13 mA.

9. IL : 50 mA.

10.dv/dt : 10 V/µs.

DEVICE SPECFICATIONS: DB-3.

Breakdown Voltage: 32V±10%

Power: 0.5 Watts.

CIRCUIT DIAGRAM :

DESIGN FOR AC VOLTAGE CONTROLLER :



Time Constant = T =RC + (R+R1)C

T should exceed the time period of half a cycle for 50Hz mains.

T =(R+R1)>=10mSec.

The resistance R1 should limit the current value ,which prevents DIAC in conduction even after

capacitor has discharged.

Therefore, R1>VBBmax/Imax : R1>=VBDIAC/IDIAC

R1>32/100ma

R1>320 ohms

Therefore , Let C=0.47 microfarads

So, 0.00000047(320+R)=15mSec

R=31900-320

=31580 ohms

Choose a 100 kilo ohms potentiometer

PROCEDURE: Make the connections as given in the circuit diagram. Switch ON the mains supply. Trigger the

TRIAC using DIAC firing circuit. Vary the firing angle potentiometer and observe the AC

voltmeter reading , waveform on the CRO & variation in lamp brightness and also note down the

voltage variation across the lamp.

For different positions ,we get different firing angle and for each setting note down the O/p voltage

ac voltmeter reading in tabular column. Plot the graph of firing angle Vs ac load voltage.

TABULAR COLUMN:


(α)=sin-1

(Vn/Vp) Vorms (Volts) Vorms (Volts)

Vrms = Vm /√2

Vorms = Vm [(π-α)/(2π) + (sin 2α)/(2π)]1/2

If α =00; then

Vorms = Vm /√2 = Virms



WAVEFORMS:

waveforms across Vsupply, capacitor (VFBO), TRIAC (VTRIAC), load(VL) with respect to

source for α = 90 degrees.

RESULT:

CONCLUSION :

We conclude that power dissipation is less in case of DIAC firing circuit than UJT firing circuit.

DIAC firing circuit has a better firing angle control than the UJT firing circuit.



8) SINGLE PHASE CONTROLLED CONVERTER

1) SINGLE PHASE SEMI CONTROLLED CONVERTER

AIM :-To conduct a suitable experiment on half controlled(semi controlled) converter with

resistive and inductive load .

APPARATUS :-

Dimmer-stat, isolator, rheostat, inductor (transformer/isolator)resistors ,single phase converter

firing circuit, SCR converter module (power circuit module) .

SINGLE PHASE CONVERTER FIRING CIRCUIT


SINGLE PHASE CONVERTER TRIGGERING UNIT - SCT

ON / OFF

90°

60°

30°

0°

120°

150°

180°

TRIGGEROUTPUTS

+ - FIRING ANGLE

T1

T '1

T 2

T '2

GND

1 2 3

7654

TEST POINTS

POWER




1. Power :- Main ON/OFF switch with built in LED Indicator.

2. Firing angle :- Potentiometer to vary the firing angle from 180°

to 0°

3. ON/OFF :- Switch for trigger output with soft start feature.

4. Test points :- To observe the signals at various points in the logic

circuit for study purpose.

5. Trigger outputs :- T1 & T11 : For +ve Half Cycle.

T2 &T21: For -ve Half Cycle.

This unit generates four line synchronized isolated triggering pulses to fire

thyristors connected in single phase (1) Half wave (2) Full wave (3) Half controlled Bridge (4)

Fully controlled Bridge and (5) AC phase control power circuit.

The firing circuit is based on Ramp-comparator scheme. Isolation is provided by

pulse transformer.

FEATURES :-

1. Work directly on 230V AC mains.

2. Gate drive current of 200mA to trigger wide range of devices.

3. Firing angle variation from 180° to 0° on a graduated scale.

4. Test points to study the logic circuit

5. Soft start and soft stop feature.

6. Neatly designed front panel.

This unit along with our SCR converter modules, rectifier diode modules, single

phase half controlled converter power circuit and single phase fully controlled

converter power circuit can be used to conduct power electronics experiments on

single phase.

BACK PANEL DETAILS :-

Mains socket with built in fuse holder.

Fuse -500mA. A spare fuse is also provided in the fuse holder.

INSTALLATION:

While operating, keep the equipment in well-aerated cool place. Avoid direct sunlight on the

equipment. Use a properly earth grounded outlet socket to connect to the equipment. This is so

because a floating earth ground will not provide a clean AC reference to the equipment. The power

input plug is situated on the back panel of the unit. Use the power cord provided along with the

equipment to the power outlet socket.

INPUT POWER SPECIFICATIONS:



Voltage : 215V -245V AC at 45 to 55Hz.

Current : 75mA (Max continuous) @ 230V AC.

500mA (Max surge).

Fuse : 500mA (Slow Blow) capsule type 20x 5mm.

Situated in the lower left corner of the equipment front panel is the power ON/OFF switch with

built in LED indicator. The LED glows when the switch is in ON position.

A fuse protects the equipment against over voltage and any short circuit. The fuse holder is an

integral part of the power inlet plug situated on the back panel. A spare fuse is provided in the fuse

holder. The power cord has to be removed from the plug, before you can access the fuse holder.

While replacing the fuse, pull off the holder smoothly.

Refer to figure shown below:

Power inlet plug

Pull here

Fuse holder

Power inlet plug/fuse holder

Remove and discard the blown off fuse and insert a new fuse in to the bay provided for it, replace

back the assembly in correct direction and press it until it flushes with the surface. Now connect

power cord back into the plug. Switch on the mains supply to the equipment. Observe the signals at

test points, trigger outputs and their phase sequence before connecting to the thyristor in the power

circuit. The built in pulse transformer based isolation between the trigger circuits and the power

circuit provides isolation up to a tune of 1000V.



5V1

1K+ 12V

10 K

100K

1K

4K7

47K

-12V

100µF

OFF/ON

+ 12V

1N 4007

1N 400710K

1K

V1S

1K

0.1

100K

4K74K7

4K74K7

555

83 7

61 25

4

P

+12V

4K7

414812K

0.010.01

7VS

4K7

P

7V5

4K7

0.01 0.01

414812K

4K7

+12V

555

6215

4

3 8 7

T1 T2

T3

4148

1K

1N 4148

4K7

4148

2N2222

22K

1N 4007

22K

1N 4007

2N2222

IN 41484148

+12V

+12V

7V5

4K7

100 K

4148

1K

1K

741

3 4

67

+12V100K

3

2

7416

7

4

+12V

1K

T4

T5

6T

15V

0.75A

15V

1N4007

1N4007

1000µF

1000µF

25V

7812

7912

1000µF

25V

1000µF

25V 25V

+12V

GND

-12V

33 /5Wς

Vun330

P/n 1K 12VBC107

SL-100

10K22PF

GATE

1K8 5V1

CAT

GATE

CAT

T

5V11K8

1N4007

FIRING ANGLE POT

CIRCUIT DIAGRAM

+ 15V

+ 15V

100K

(75mA)

0

+12V

-12V

T7

1N4007

1'

T1

0.1µF

0.1µF



TEST POINTS

1

2

3

Vc 4

5

6

7

8

T1 & T1

T2 & T2

TRIGGER OUTPUTS



SERVICING DETAILS

SINGLE PHASE CONVERTER FIRING CIRCUIT :

a) Check the 3 pin Mains Cable used along with this unit

b) Check the Fuse in the Mains socket

c) Check the Mains Switch

d) Check the transformer

e) Check the firing angle potentiometer.

f) Check the ON/OFF switch

g) Check the zener diodes & IN4007 diodes at the output of the pulse transformer.

h) Check +12V & -12v power supply (Check 7812 &7912 regulators)

i) Check BC 107 & SL 100 transistors

j) Check 2N2222 transistors

k) Check 741/555IC’s

l) Check for any loose contacts.

SINGLE PHASE SEMI CONTROLLED CONVERTER POWER CIRCUIT :

SPECIICATIONS, 230V/5A

The circuit arrangement of a single-phase full converter is shown in fig. During the positive half

cycle, thyristor T1 and T11 are forward biased; and when these two thyristor are fired

simultaneously at wt=α, the load is connected to the input supply through T1 and T11 . In case of

inductive loads, during the period π ≤ wt ≤ (π+α), the input voltage is negative and the

freewheeling diode Dm is forward biased. Dm conducts to provide the conductivity of current in the

inductive load. The load current is transferred from T1 to Dm; and thyristor T1 IS turned off due to

line or natural commutation.

During the negative half cycle of the input voltage, thyristor T2 is forward

biased. The firing of thyristor T2 at wt= π+α will reverse bias Dm.

The diode Dm is turned off and the load is connected to the supply through T2 and T21.

Figure shows the waveforms for input voltage, output voltage and Trigger Outputs.




This power circuit consists of four SCRs connected as semi- controlled bridge converter. A free

wheeling diode is provided to observe the effect of free wheeling diode on inductive loads.

Each device in the unit is mounted on an appropriate heat sink and is protected by snubber circuit.

Short circuit protection is achieved using glass fuses. A circuit breaker is provided in series with

the input supply for overload protection and to switch ON/OFF the supply to the power circuit.

The front panel consists of input and output terminals. The gate and Cathode of each SCRs brought

out on the front panel for firing pulse connection. Voltmeter and an Ammeter is mounted on the

front panel indicates the output voltage and current. A separate full wave bridge rectifier is

provided in the unit to get the DC supply for the field of DC Shunt Motors. The power circuit

schematic is printed on the front panel.

SPECIFICATIONS: Input Voltage :15V to 230V AC.

Load current : 5 Amps maximum

Fuses : 6 Amps fast blow glass fuses.

Field supply : 220V ± 10%/2 Amps

MCB : Two pole 6 Amps/ 230V

FRONT PANEL DETAILS: Input terminals : To connect single phase input supply.

Output terminals(+&-) : To connect load.

Voltmeter(0 to 300V) : To indicate output voltage

Ammeter(0 to 5A) : To indicate output current.

Circuit breaker : 6 Amps AC power ON/OFF to the circuit and for

protection .

T1 & T2 : SCR – 16 TTS 12-16 A rms/1200Volts.

D1 & D2 : Diodes –SPR 16PB-16A/1200V

DM : Free wheeling diode –SPR 16PB-16A/1200V

Field(+ and -) : Field supply for DC motor for motor control

(with indicator) experiments.

BACK PANEL DETAILS: Mains socket : For 230V AC mains supply to field supply bridge rectifier.

Fuse holders : 2 fuses in series with input AC supply, a fuse at the output and a fuse for

free wheeling diode.Fuse - 6 Amps

SINGLE PHASE POWER CIRCUIT

BLOCK DIAGRAM: :

230 V ,50Hz 0-230V

Isolation

Transformer

Power

Circuit

Load Dimmer

Stat

Firing

circuit



1. Isolation Transformer:

To suit single phase 230V/50Hz supply, ratio 1:1, KVA rating to suit the load rating with

tapping at different voltages. Isolation of mains, phase and neutral with measurement circuit.

Serves the purpose of di/dt protection of SCR’s and safe measurement of waveforms by using

oscilloscope. Isolation of Electric noise with mains.

2. Power circuit:

Different power circuit configurations are possible using SCR’s and diode modules.

Half Wave Converter – 1SCR

Half Controlled Converter _ 2 SCRs & 2 Diodes

AC phase Control – 2 SCRs

3. Firing Circuit:

Each SCR of the above Power Circuit to be triggered using independently isolated outputs

using single phase converter firing unit. Trigger outputs phase sequence and variation to be

checked before with the power circuit. Phase sequence to be compared with the power circuits

phase sequence.

PROCEDURE :-

Switch on the mains to the circuit. Observe all the test points by varying the firing angle

potentiometer and trigger o/p’s ON/OFF switch. Then observe the trigger o/p’s and their phase

sequence .Make sure that all the trigger o/p’ sure proper before connecting to the power circuit..

Next connections in power circuit .Use a dimmer stat with a isolator and connect it to power

circuit. Connect the R-load between load points .Connect firing pulses from the firing circuit to

respective SCR’s .Switch ON the MCB trigger o/p’s and note down load voltage can be seen

.Repeat this same for R-L load and with and note down waveform.



TABULAR COLUMN:


(α)=sin-1

(Vn/Vp) Vodc (Volts) Vodc (Volts)

Vodc (th) = Vm (1+cos α) /π

Free Wheeling Diode, Resistive Load, and Resistive and Inductive load



WAVEFORMS:



RESULT:-

CONCLUSION :- The output voltage at various firing angles are noted with R load and RL load and the difference

with and without free wheeling diode is observed. The relevant waveforms are traced.



(ii) SINGLE PHASE FULLY CONTROLEED CONVERTER

AIM: To Study the Single Phase Fully Controlled Converter on Resistance, Resistance &

Inductance Loads .

APPARATUS: Single Phase Converter Firing Circuit, Single Phase Fully controlled Power circuit,

Rheostat (150 Ohms/5A), Inductor(150 mH/5A), Power Scope, Connecting Wires etc.,

SINGLE PHASE CONVERTER FIRING CIRCUIT


SINGLE PHASE CONVERTER TRIGGERING UNIT - SCT

ON / OFF

90°

60°

30°

0°

120°

150°

180°

TRIGGEROUTPUTS

+ - FIRING ANGLE

T1

T '1

T 2

T '2

GND

1 2 3

7654

TEST POINTS

POWER

FRONT PANEL DETAILS: 1. Power :- Main ON/OFF switch with built in LED Indicator.

2. Firing angle :- Potentiometer to vary the firing angle from 180°

to 0°

3. ON/OFF :- Switch for trigger output with soft start feature.

4. Test points :- To observe the signals at various points in the logic

circuit for study purpose.

5. Trigger outputs :- T1 & T11 : For +ve Half Cycle.

T2 &T21: For -ve Half Cycle.

This unit generates four line synchronized isolated triggering pulses to fire

thyristors connected in single phase (1) Half wave (2) Full wave (3) Half controlled Bridge (4)

Fully controlled Bridge and (5) AC phase control power circuit.

The firing circuit is based on Ramp-comparator scheme. Isolation is provided by pulse transformer.



FEATURES :- 1. Work directly on 230V AC mains.

2. Gate drive current of 200mA to trigger wide range of devices.

3. Firing angle variation from 180° to 0° on a graduated scale.

4. Test points to study the logic circuit

5. Soft start and soft stop feature.

6. Neatly designed front panel.

This unit along with our SCR converter modules, rectifier diode modules, single

phase half controlled converter power circuit and single phase fully controlled

converter power circuit can be used to conduct power electronics experiments on

single phase.

BACK PANEL DETAILS :-

Mains socket with built in fuse holder.

Fuse -500mA. A spare fuse is also provided in the fuse holder.

INSTALLATION:

While operating, keep the equipment in well-aerated cool place. Avoid direct sunlight on the



input plug is situated on the back panel of the unit. Use the power cord provided along with the


Input power specifications:

Voltage : 215V -245V AC at 45 to 55Hz.

Current : 75mA (Max continuous) @ 230V AC.

500mA (Max surge).

Fuse : 500mA (Slow Blow) capsule type 20x 5mm.

Situated in the lower left corner of the equipment front panel is the power ON/OFF switch with

built in LED indicator. The LED glows when the switch is in ON position.

A fuse protects the equipment against over voltage and any short circuit. The fuse holder is an


holder. The power cord has to be removed from the plug, before you can access the fuse holder.


Refer to figure shown below:

Power inlet plug

Pull here

Fuse holder




Remove and discard the blown off fuse and insert a new fuse in to the bay provided for it, replace

back the assembly in correct direction and press it until it flushes with the surface. Now connect

power cord back into the plug. Switch on the mains supply to the equipment. Observe the signals at

test points, trigger outputs and their phase sequence before connecting to the thyristors in the power

circuit.

The built in pulse transformer based isolation between the trigger circuits and the power circuit

provides isolation up to a tune of 1000V.

Note that T1- T11 and T2- T2

1are from different secondary. Therefore T1 –T1

1 will be in phase and

T2-T21 in the opposite phase.

The table below gives the usage of the trigger output against different experiments.

SL.NO EXPERIMENT TRIGGER OUTPUTS

T1 T1’ T2 T2’

1 I –Phase half wave converter *

2 I –Phase full wave converter * *

3 I –Phase half controlled converter * *

4 I –Phase full controlled converter * * * *

5 I –Phase AC, phase control * *

5V1

1K+ 12V

10 K

100K

1K

4K7

47K

-12V

100µF

OFF/ON

+ 12V

1N 4007

1N 400710K

1K

V1S

1K

0.1

100K

4K74K7

4K74K7

555

83 7

61 25

4

P

+12V

4K7

414812K

0.010.01

7VS

4K7

P

7V5

4K7

0.01 0.01

414812K

4K7

+12V

555

6215

4

3 8 7

T1

T2

T3

4148

1K

1N 4148

4K7

4148

2N2222

22K

1N 4007

22K

1N 4007

2N2222

IN 41484148

+12V

+12V

7V5

4K7

100 K

4148

1K

1K

741

3 4

67

+12V100K

3

2

7416

7

4

+12V

1K

T4

T5

6T

15V

0.75A

15V

1N4007

1N4007

1000µF

1000µF

25V

7812

7912

1000µF

25V

1000µF

25V 25V

+12V

GND

-12V

33 /5Wς

Vun330

P/n 1K 12VBC107

SL-100

10K22PF

GATE

1K8 5V1

CAT

GATE

CAT

T

5V11K8

1N4007

FIRING ANGLE POT

CIRCUIT DIAGRAM

+ 15V

+ 15V

100K

(75mA)

0

+12V

-12V

T7

1N4007

1'

T1

0.1µF

0.1µF



TEST POINTS

1

2

3

Vc 4

5

6

7

8

T1 & T1

T2 & T2

TRIGGER OUTPUTS



SERVICING DETAILS

SINGLE PHASE CONVERTER FIRING CIRCUIT :

a) Check the 3 pin Mains Cable used along with this unit

b) Check the Fuse in the Mains socket

c) Check the Mains Switch

d) Check the transformer

e) Check the firing angle potentiometer.

f) Check the ON/OFF switch

g) Check the zener diodes & IN4007 diodes at the output of the pulse transformer.

h) Check +12V & -12v power supply (Check 7812 &7912 regulators)

i) Check BC 107 & SL 100 transistors

j) Check 2N2222 transistors

k) Check 741/555IC’s

l) Check for any loose contacts.

SINGLE PHASE FULLY CONTROLLED CONVERTER POWER CIRCUIT : SFC-

230V/5A

The circuit arrangement of a single-phase full converter is shown in fig. During the positive half

cycle, thyristor T1 and T11 are forward biased; and when these two thyristor are fired

simultaneously at wt=α, the load is connected to the input supply through T1 and T11 . In case of

inductive loads, during the period π ≤ wt ≤ (π+α), the input voltage is negative and the

freewheeling diode Dm is forward biased. Dm conducts to provide the conductivity of current in the

inductive load. The load current is transferred from T1 and T11 to Dm; and thyristor T1 and T1

1 are

turned off due to line or natural commutation.

During the negative half cycle of the input voltage, thyristor T2 and T2

1are forward

biased. The firing of thyristor T2 and T21

simultaneously at wt= π+α will reverse bias Dm.

The diode Dm is turned off and the load is connected to the supply through T2 and T21.

Figure shows the waveforms for input voltage, output voltage and Trigger Outputs.


A +

S H CF IE L D

O N

L IN E

R E C T IF IE R

~

+

~

-

1 P h . IN

N

L

-

T 1 T 2

V

D m

1 P h . F U L L Y C O N T R O L L E D C O N V E R T E R P O W E R C I R C U I T

T 1 'T 2 '

N

L

M C B

A M M E T E R

M E T E R

V O L T



This power circuit consists of four SCRs connected as fully controlled bridge converter. A free

wheeling diode is provided to observe the effect of free wheeling diode on inductive loads.

Each device in the unit is mounted on an appropriate heat sink and is protected by snubber circuit.

Short circuit protection is achieved using glass fuses. A circuit breaker is provided in series with

the input supply for overload protection and to switch ON/OFF the supply to the power circuit.

The front panel consists of input and output terminals. The gate and Cathode of each SCRs brought

out on the front panel for firing pulse connection. Voltmeter and an Ammeter is mounted on the

front panel indicates the output voltage and current. A separate full wave bridge rectifier is

provided in the unit to get the DC supply for the field of DC Shunt Motors. The power circuit

schematic is printed on the front panel.











protection .

T1,T11,T2 & T2

1 : SCR – 16 TTS 12-16 A rms/1200Volts.






free wheeling diode.

Fuse - 6 Amps

SINGLE PHASE POWER CIRCUIT Single ph AC

Input

Single Phase Experiments Block Diagram

Isolation

Transformer

Power

Circuit

Load

Firing

Circuit



1.Isolation Transformer :-


tappings at different voltages. Isolation of mains, phase and neutral with measurement circuit.



2.Power circuit :



Full Wave converter – 2 SCRs


Fully Controlled Converter – 4 SCRs


3. Firing Circuit :




phase sequence.

4. Load :

Load connection should include an ammeter and a current shunt for current waveform

measurements. Use freewheeling diodes wherever necessary.

Types of Loads: -

a) Resistance – ‘R’

b) Resistance and Inductive load ‘R’ & ‘L’.

c) Motor and Generator.

Note: In case of DC motor control, field excitation is separate. Field supply should be ON before

giving armature supply. It should be switched OFF only after switching off the armature supply.

Lamp load: Due to di/dt limitation of SCR’s and since the initial inrush current

is 20 to 25 times more than load current in lamp loads and also since the cold resistance of the lamp

is very less, lamp loads can be used with large safety factors.

Precaution: Initially keep the input voltage low and firing angle at 1800.Slowly increase the

voltage to the rated voltage and firing angle to 00.



CIRCUIT DIAGRAM:

INSTRUCTIONS: 1. Check all the SCRs for performance before making the connections.

2. Check the firing circuit trigger outputs and its relative phase sequence.

3. Make fresh connections before you make a new experiment.

4. Preferably work at low voltages (20-30V) for every new connections. After careful verification it

can be raised to the maximum ratings. (This is to reduce damages due to wrong connections and

high starting current problems).

5. The thyristor has a very low thermal inertia as compared to machine and by any overload or

short circuit the SCR will immediately get damaged. Therefore do not switch ON the supply until

the instructor has checked the connections.

6. While observing the waveforms of two parameters on the oscilloscope, either differential input

oscilloscope should be used or special differential modules should be used with normal

oscilloscope. On normal oscilloscope, observation of wave forms can be done with respect to single

common point only. Ground connections of other probe must be avoided. It will lead to short

circuit if ground connections of both the probes are used since they are internally shorted. In no

case should oscilloscope input ground point be disconnected. This is a dangerous practice. Use 10:1

oscilloscope probe to see the waveforms at high voltages.

7. Do not make Gate & Cathode measurements when the power circuit is ON.

TABULAR COLUMN:


(α)=sin-1


Vodc (th) = 2Vm (cos α) /π



PARAMETERS AND OBSERVATIONS: 1. Input voltage waveform

2. Output Voltage waveform (across the load)

3. Output current waveform (through the shunt)

4. Voltage waveform across thyristors (make this measurement only if isolations is used)

5. Study of variation of voltage and current waveforms with the variation of firing angle.

6. Study of effect of freewheeling diode in case of inductive loads.

WAVEFORMS:

0

Wt

Wt

Wt

Wt

VmV

V=VmSin wt

2 ππ π + αα

α π π + απ20

T 1

2T

Vo

VOLTAGE WAVE FORMS



RESULT:

CONCLUSION: The output voltage at various firing angles are noted with R load and RL load and the difference




SERVICING DETAILS:

Single-phase fully- controlled converter:

Power circuit: - a) Check the devices – SCRs and diodes.

b) Check the fuse.

c) Check the MCB.

d) Check for any loose contacts.

e) Check the field supply bridge rectifier.



9) VOLTAGE COMMUTATED (IMPULSE COMMUTATED CHOPPER) BOTH

CONSTANT FREQUENCY AND VARIABLE FREQUENCY

AIM: To rig up DC Jones Chopper and to control O/P average DC Voltage both at constant

frequency and variable frequency and at different duty cycles.

APPARATUS: DC chopper power circuit ,DC chopper firing circuit, DC Regulated power supply (0-30V/2A),

Rheostat (100hms/2A), CRO, connecting wires.

DESCRIPTION :

DC CHOPPER FIRING CIRCUIT:

This firing unit provides triggering pulses for the Thyristors in auxiliary commuted chopper circuit

configurations. It can be used for voltage commutation and current commutation chopper circuits

consisting of one main load carrying Thyristor and one auxiliary Thyristor and associated

commutation components.

DC – Chopper firing unit should be used together with our DC-Chopper power circuit to conduct

DC-DC chopper experiments on resistance, resistance and Inductance and motor load.

This firing circuit can also used for other chopper circuits also.

SPECIFICATIONS:

Power supply : 230V/50 Hz, single phase ac mains.

Output : Two pulse Transformer isolated trigger pulses for

main and auxiliary Thyristors.

Gate Drive current : 200 mA

Auxiliary Gate pulse width :100µsec.

Main Gate pulse width : Train of pulses

Test points : 1 to 8 provides signals at various points of the logic circuit.

Duty cycle : Variation from 10% to 90%.

Frequency : Variation from 30 Hz to 300 Hz. Approximately.

Control Voltage : Variation from 0 to 5V when the control switch is in INT position. External

control voltage can be used by putting the switch to EXT position.




DC - CHOPPER TRIGGERING UNIT - DCT

10%

TRIGGEROUTPUTS

90%

DUTY CYCLE

Max.Min.

FREQUENCY

+ -

T M A IN

T A U X

G N D

1 2 3

7654

T E S T P O IN T S

P O W E R


Power : ON/OFF switch with built-in indicator.

Test points :1-7 test points for study of firing circuit.

Duty cycle : Potentiometer to vary the duty cycle from 10% to 90% when the control

switch is at INT position at the set frequency .

Frequency : Potentiometer to vary the operating frequency of the chopper from 30Hz to 300Hz

approximately.

ON/OFF : Switch for main thyristor trigger pulse with soft start feature.

Trigger Output TM : Main Thyristor Trigger pulse – Train of pulses.

Trigger Output TA. : Auxiliary Thyristor Trigger pulse of 100 µsec.

BACK PANEL DETAILS:

Main socket with built in fuse holder.

Fuse – 500mA.



NOTES:

1. The chopper cannot be tested without connecting the load.

2. The main thyristor T1 has to carry the resonant reversal current (along with load

current) there by increasing current rating requirements.

3. The discharging and charging time of commutation capacitor are dependent on the load

current and this limits the high frequency operation, especially at low load current.

4. The maximum value of the duty cycle is also limited to allow the commutation

capacitor to discharge and recharge.

5. The thyristor T1 must be ON for a minimum time of tr = π(LmC) to allow the charge

reversal of the capacitor and tr is fixed for a particular circuit design. This imposes

minimum duty cycle limit and hence minimum output voltage.

6. The firing circuit provides the trigger pulses in the following range:

Duty cycle: 10% to 90%

Frequency: 30Hz to 300Hz.

When the frequency is varied, the duty cycle is maintained constant at the set value. For example if

the duty cycle is 50% at 50 Hz and you have now selected the frequency to vary from 50 Hz to 100

Hz, the duty cycle still remains 50% at 100Hz.

The range of chopping frequency/duty cycle provided is no guarantee that any chopper power

circuit will work for the full range. The limits of operation of a given power circuit depend on

various factors like (a) the turn off requirement of the main thyristor (which should be less than the

available turn off time) (b) the peak load current (c) the input DC voltage (d) The source and load

inductance (e) The commutation circuitry – the value of C and Lm, etc.,

The function of firing circuit is only to provide properly sequenced and accurately timed trigger

pulse in the said range. The trigger pulse for the main thyristor T1 is a continuous train of pulses

for the whole of the ‘ON’ time kT (where k is the duty cycle). This train of pulses will be followed

by the firing pulse for commutation thyristor, also known as Auxiliary thyristor, T2. This auxiliary

trigger pulse is a single pulse whose width is approximately 100 microseconds.

INSTALLATION:

While operating, keep the equipment in well-aerated cool place. Avoid direct sunlight on to the



input plug is situated on the back panel of the unit. Use the power card provided along with the


INPUT POWER SPECIFICATIONS:

Voltage : 215 – 245 A/C at 45 to 55 Hz.

Current : 75mA (Max. continuous)@ 230V A/C.

500mA (Max. surge.)

Fuse : 500mA (Slow Blow) Capsule type 20 x 5mm.

Situated in the lower left corner of the equipment font panel is the power ON/OFF switch with

built-in in LED indicator. The LED glows when the switch is in ON position.



A fuse protects the equipment against over Voltages and any short circuit. The fuse holder is an


holder. The power card has to be removed from the plug, before you can access the fuse holder.


Refer to the figure shown below.

Power inlet plug

Pull here

Fuse holder


Remove and discard the blown off fuse and insert a new fuse in to the bay provided for it, Replace

back it the assembly in correct direction and press it until it flushes with the surface. Now connect

the power card back into the plug. Switch on the mains supply to the equipment. Observe the test

point’s signals, Trigger outputs and their phase sequence before connecting to the thyristors in the

power circuits.

DESIGN FOR JONES CHOPPER (VGE COMMUTATED CHOPPER)

Ic = Cdv/dt; -(1);

Ic = capacitor current

v=Voltage across capacitor

for constant load current ; equation can be

Ic = CVs/tc or C = tcIo/Vs

tc= commutating circuit time>tq(device turn-off time)

i.e,tc>tq ; so now let tc = tq + ∆t

tq for TY612 is 70 µSec which is almost equal to100 µSec

Let ∆t= 20 µSec

Therefore tc = 120µSec

Let Vs= 30v; Ic =2 A.

Therefore c = 120 µSec x 2/30

= 4 x 2 µF = 8 µF.

Choose C = 10 µF.



Ic = VsSin (Wot)/Wo L ;

Wo = 1/[LC] ½

Icp = Vs/WoL<=Io

<=Vs[(C/L)] ½

,

L>=[ (Vs/Io)]2

C >= [ (30/2)]2 8 x 10

-6 >=1.8mH

Select L= 2mH or 8mH.

WAVEFORMS:

15 T P1

0

10V

5 T P2

5V

0 T P3

D C - C H O P PE R F IR IN G C IR C U IT - T E ST PO IN T S

5V

0 T P 4

5V

0 T P 5

0 T P 6

5V

T P 7

T

T A

M

JONES CHOPPER POWER CIRCUIT: 30V/2A:

This unit consists of two SCR’s two diodes and L C commutation circuit to construct Jones chopper

power circuit. Each device in the unit is mounted on an appropriate hear sink and is protected with



an RC snubber circuit. All the components are independent and their connections are brought out

to front panel. The cathode and gate of each SCR is brought out ob to separate terminals for firing

pulse connection. A switch and a fuse are provided in series with the input DC Supply.

The devices and components can also be used to build different chopper circuits. Integrated

Thyristor Controller –ITC 08 and DC chopper firing unit DCT provided triggering pulses for this

power circuit.

SPECIFICATION:

30V @ 2.0 Amps.


+

+

-

DC INPUT

L

L'

C com

TM

TA DFW

D1

OUTPUT

+

-

RECTIFIER

~

+

~

-

230 VAC

FIELD

SCR DC - CHOPPER POWER CIRCUIT - SDCP

MC B

FRONT PANEL DETAILS: VDC IN : Terminal to connect DC input 10V to 30V DC.

ON : ON/OFF switch for the input DC supply to the power circuit.

Fuse : In series with the DC input for short circuit protection –2 Amps.

T1 & T2 :SCR’s – TYN 616

D1 & D2 : diodes – BYQ 28 200.

C : Commutation Capacitor – 10uF/100V.

L1-0-L2 : Commutation Inductor 500-0-500 Micro henry/2 Amps.



CIRCUIT DIAGRAM:

PROCEDURE :

To begin with switch ON the DC Chopper firing unit. Observe the test point Signals and Trigger

output signals by carrying Duty cycle and Frequency Potentiometer by keeping the control switch

into INT position. Be sure the trigger Outputs are proper before connecting to the power circuit.

Now make the interconnections in the power circuit as given in the circuit diagram. Connect DC



supply from a variable DC source. Initially set the input DC supply to 10 Volts. Connect a

Resistive load. Connect respective trigger outputs from the firing circuit to the respective SCRs in

the Power circuit. Initially keep[ the ON/OFF switch in the firing circuit in OFF position.

Switch ON the DC supply. Apply Main SCR trigger pulses by pressing the ON/OFF Switch to ON

position. Observe the voltage waveforms across load. We can observe the chopped DC waveform.

If the commutation fails we can see only the DC voltage. In that case switch OFF the DC supply,

Switch OFF pulses and check the connections and try again. Observe the voltage across load,

across Capacitor, across Main SCR and auxiliary SCR by varying Duty cycle and frequency

Potentiometer. Now vary the DC supply up to the rated voltage (30V DC). Draw the waveforms at

different duty cycle and at different Frequency. Connect Voltmeter and Ammeter and note down

values in the table.

TABULAR COLUMNS:

Sl.

No.

V in

Volts

Ton

Secs.

Toff

Secs.

Duty

cycle

Vo(volts) Practical

Vo(volts) Theoretical

INSTRUCTIONS:

1. Check all the SCR’s for performance before making the connections.

2. Check the firing circuit Trigger output and its relative phase sequence

3. Make fresh connection before you make a new experiment.

4. Preferably work at low voltages for every new connections. After careful verification

it can be raised to the maximum ratings (This is to reduce damages due to wrong

connections and high starting current problems)

5. The Thyristor has a very low thermal inertia as compared to machine and by any over

load or short circuit the SCR will immediately get damaged. Therefore do not switch

ON the supply until the instructor has checked the connections.

6. While observing the waveform of two parameters on the oscilloscope observation of

waveforms can be done with respect to single common point only. Ground connection

of other probe must be avoided. It will lead to short circuit if ground connections of



both the probes are used. Since they are internally shorted. In no case should

oscilloscope input ground point be disconnected. This is a dangerous practice. Use

10:1 oscilloscope probe to see the waveforms at high voltages.

7. Do not make Gate & cathode measurements when the power circuit is on

PARAMETERS AND OBSERVATIONS: 1. Voltage wave form across capacitor.

2. Output voltage waveforms (across the load)

3. Output current waveforms (Through the shunt)

4. Voltage waveforms across Thyristor.

5. Study of variation of voltage and current waveforms with the variation of duty cycle

and frequency.

6. Study of effect of free wheeling diode in case of inductive loads.

PRECAUTIONS: 1.In case of DC motor control, field excitation is separate. Field supply must be ON

before giving armature supply. It should be OFF only after switching off the armature

supply. Without field supply load current is too high which is limited by armature

resistance.

2.In case lamp load, due to di/dt limitation of SCR’s and since the initial inrush current

is 20 to 25 times more than load current, it can be done only with large safety factor.

3.Chopper cannot be tested without connecting load.

RESULT:

CONCLUSION : The chopper has been verified and tested .It is found that Vo(prac) = Vo(theor)



10) SPEED CONTROL OF SEPARATELY EXCITED DC MOTOR:











protection .

T1,T11,T2 & T2

1 : SCR – 16 TTS 12-16 A rms/1200Volts.






free wheeling diode.

Fuse - 6 Amps



1.Isolation Transformer :-


tappings at different voltages. Isolation of mains, phase and neutral with measurement circuit.



2.Power circuit :



Full Wave converter – 2 SCRs


Fully Controlled Converter – 4 SCRs


3. Firing Circuit :




phase sequence.

4. Load :

Load connection should include an ammeter and a current shunt for current waveform

measurements. Use freewheeling diodes wherever necessary.

Types of Loads: -

a) Resistance – ‘R’

b) Resistance and Inductive load ‘R’ & ‘L’.

c) Motor and Generator.

Note: In case of DC motor control, field excitation is separate. Field supply should be ON before

giving armature supply. It should be switched OFF only after switching off the armature supply.

Lamp load: Due to di/dt limitation of SCR’s and since the initial inrush current

is 20 to 25 times more than load current in lamp loads and also since the cold resistance of the lamp

is very less, lamp loads can be used with large safety factors.

Precaution: Initially keep the input voltage low and firing angle at 1800.Slowly increase the

voltage to the rated voltage and firing angle to 00.

INSTRUCTIONS: 1. Check all the SCRs for performance before making the connections.

2. Check the firing circuit trigger outputs and its relative phase sequence.

3. Make fresh connections before you make a new experiment.



4. Preferably work at low voltages (20-30V) for every new connections. After careful verification it

can be raised to the maximum ratings. (This is to reduce damages due to wrong connections and

high starting current problems).

5. The thyristor has a very low thermal inertia as compared to machine and by any overload or

short circuit the SCR will immediately get damaged. Therefore do not switch ON the supply until

the instructor has checked the connections.

6. While observing the waveforms of two parameters on the oscilloscope, either differential input

oscilloscope should be used or special differential modules should be used with normal

oscilloscope. On normal oscilloscope, observation of wave forms can be done with respect to single

common point only. Ground connections of other probe must be avoided. It will lead to short

circuit if ground connections of both the probes are used since they are internally shorted. In no

case should oscilloscope input ground point be disconnected. This is a dangerous practice. Use 10:1

oscilloscope probe to see the waveforms at high voltages.

7. Do not make Gate & Cathode measurements when the power circuit is ON.

8. Vary the firing and note down Vodc, Iodc and speed N in RPM

TABULAR COLUMN:

Firing on the

Pottetiometer

Deg

Firing angle Practical Theoretical N Speed in RPM

(α)=sin-1


Vodc (th) = 2Vm (cos α) /π

PARAMETERS AND OBSERVATIONS: 1. Input voltage waveform

2. Output Voltage waveform (across the load)

3. Output current waveform (through the shunt)

4. Voltage waveform across thyristors (make this measurement only if isolations is used)

5. Study of variation of voltage and current waveforms with the variation of firing angle.

6. Study of effect of freewheeling diode in case of inductive loads.

7. Fro various firing note the speed on the digital meter on the motor panel.



WAVEFORMS:

0

W t

W t

W t

W t

V mV

V =V m S in w t

2 ππ π + αα

α π π + απ20

T 1

2T

V o

V O L T A G E W A V E FO R M S



RESULT:

CONCLUSION: The output voltage at various firing angles are noted with DC Motor as load and the difference




11) SPEED CONTROL OF UNIVERSAL MOTOR Motor Specification: 0.5HP/220V AC/DC

AIM: To Control the speed of the Universal through (i) AC-DC Power converter (FCR) and

(ii)AC Voltage Controller

Apparatus: Universal Motor, Isolation Transformer, dimmer-stat, Fully controlled bridge

rectifier (FCR), ACVC, FCR Firing Circuit.



Procedure: Make the inter connections in the power circuit as in the circuit for FCR and ACVC,.

Switch on the the firing circuit and observe the trigger pulses. Make sure that the firing pulses are

proper before connecting to the power circuit. Then connect the trigger output from the firing

circuit to the corresponding SCR’s/TRIAC. In the power circuit initially set AC input to 30V.

Switch on the MCB. Switch on the trigger. First observe the output across R load by varying the

potentiometer. If the output wave form is proper then you can connect the motor and increase the

input voltage to the rated value i.e., 230V gradually. Vary the firing angle and note O/P voltage

and speed of the motor

Table (Fully Controlled Rectifier

Firing on the

Potentiometer

Deg


(α)=sin-1


Table (ACVC)

Firing on the

Potentiometer

Deg


(α)=sin-1

Vn/Vp) Vodc (Volts) Vodc (Volts)



12) SPEED CONTROL OF STEPPER MOTOR:

STEPPER MOTOR CONTROLLER

This is Micro controller based controller circuit to accurately generates pulses to energizes the

stepper motor winding in the desired sequence . Power transistor based driver circuit to driver

circuit to drive the stepper motor. From this controller we can set the speed of the stepper motor in

RPM, set the number of steps motor can move .We can set the direction of rotation forward and

reverse direction. We can also set half step and full step mode.


1.Mains :Power ON/Off Switch to the unit with built-in indicator.

2.Display :Seven segment 5 digit display to display the parameter and values

3.Key board :

a)Set :To set the Parameter.

b)INC :To increment the set parameter values.

c)DEC :To decrement the set parameter values.

d)ENT :To enter the set values.

e)RUN/STOP :To start and stop the stepper motor. .(Built in)

4.+v : 5v/2 amps DC supply for stepper motor.(Built in)

5.+5v :5 v for control circuit .(Built in)

6.GND :Supply ground point

7.FUSE :2 amp fast below glass fuse for short circuit protection.

8.A1,A2,B1 & B3: Outpoints to connect to the A1,A2,B1 &B3 leads of stepper motor.

9.LED’s :To indicate the status of output.

BACK PANNEL DETAILS:

Mains socket with built in fuse holder and a spare fuse.

PROCEDURE:-

Connect A1, A2, B1 and B2 leads of stepper motor to the corresponding output terminal points.

And two common terminal to +V supply. Switch ON the mains supply to the unit. Check the

power supplies. The unit display S – 00. Now press SET. Then the display shows rpm(revolutions

per minute). If you press ENT now the speed mode is set and it displays 00. Then press INC Key to

set the rpm. When the display shows rpm, if you press INC/DEC it goes to STEP mode or vice

versa.

After setting the Speed in rpm/ no of steps, press ENT Key. Then the parameter values is entered

and it shows set direction of rotation. Press INC/DEC changes the direction of rotation. Then press

ENT Key to set the direction of rotation.

Then it displays Half step or Full step mode. Pressing INT/DEC will changes to HALF Step/ FULL

Step mode or vice versa. Press ENT Key to set the Half step or Full step mode.



Then it displays n-set rpm if speed is selected or S-set steps if steps is selected. This is the method

for setting the parameter. After this if we press RUN/STOP key the Motor stops.

If we select the STEP mode the motor moves the number of set steps and stops when we press

RUN/STOP key. If we press again the motor moves again and stops.

Set the step mode at 1 step and half step mode and check the output status by LED indication for

each step of rotation and verify with the theoretical.

Repeat the same foe Full step mode also.

Repeat the above for the other direction.

D.C.BRUSHLESS STEPPING MOTORS

The stepping motor is an electromagnetic device which converts digital pulses into discrete

mechanical rotational movements. In rotary stepper motor, the output shaft of motor rotates in

equal increments, in response to a train of input pulses.

CHARACTERISTICS:-

Construction:-

Stepping Motor is basically a Motor with two phases, eight salient poles, toothed iron rotor and a

permanent magnet. This rotor is known as hybrid rotor. The rotor is suspended in the stator by

means of sealed ball bearings. All parts of the motors are precision machined for better

performance and accuracy of steps.

Step Angle: 1.8*+ or - .1* non-cumulative.

Holding Torque: 2.8 Kg cm.

Dynamic Torque: Dynamic torque is mainly controlled by the electronic control circuits.

Torque will drop down as the speed increases.

Residual Torque or Detent Torque : Because of the presence of permanent magnet in the rotor.

Working Temperature and insulation Class: Temperature of stepping motors may rise 50*C above

ambient. It is observed that body temperature generally stabilizes at about 85*C to 90*C for

continuous duty cycle. The insulation used is of class B type which can withstand hot spot temp of

130*C. For better heat dissipation motors duly fitted with heat sinks are recommended. This

reduces the temp by about 10*C to 15*C.

Working of stepping motor:-

The stepping action is caused by sequential switching of supply to the two phases of motor as

shown in switching logic sequence table. The specified torque of any stepping motors is the torque

at stand still (holding torque). This torque is directly proportional to the current to rated level within

the time given for one step.

This is mainly due to L/R time constant of winding. The drop in current level causes drop in torque

as the speed increases. In order to improve torque at high speed it is necessary to maintain current

at the rated level.

Never exceed rated current of the motor.

Stepping Motors differ form conventional DC Servo Motors in the following respects.

1.There is no control winding in stepping Motors. Both windings are identical.

2.The stepping rate (speed of rotation) is governed by frequency is governed by frequency of

switching and not by supply voltage.



3.A single pulse input will move the shaft of motor by one step. Thus number of steps can be

precisely controlled by controlling number of pulses.

4.When there is no pulses input, the rotor will remain locked in the position in which the last step

was taken since at any time two winding are always energized which lock the rotor electro

magnetically.

5.Steping Motors can be programmed in there parameters namely :

a) Direction.

b) Speed.

c) Number of steps.

6.Stepping Motor is brush less so no wear & tear.

7.Load & no load condition makes no difference in running currents of the motor.

GENERAL INFORMATION:-

1.Resonance – When a stepping motor is operated at its natural frequency an increase in noise and

vibration occurs. This phenomenon is called as resonance. The frequencies at which this resonance

occurs depends widely on the characteristic of load and it also varies from motor to motor. The

change in inertial load will; change the resonance frequency. In half-step mode resonance may be

reduced / avoided.

2.Ramp – Acceleration (soft start) and declaration (soft stop are essential factors of controller .

Acceleration is required to run the motor at high step rates and declaration is to stop motor

accurately at specified position.

3.Half Step Mode – Advantage – Smother motion ,resolution factor increases by the factor2,

reduces resonance problems. Disadvantages-Loss of torque(above 40%) In half step mode we do

not offer guarantee for accuracy but error automatically gets corrected on next even half step.

4. Mounting-Flange Mounting. Motor must be mounted with reference to boss and not with

reference to mounting holes.

5. Synchronization-‘N’ no. of SRI.SYN. Stepper motors can be operated simultaneously at time

with single controller &’N’ no. of drives.

APPLICATION:-

Numerically controlled Machine Tools and Machining centers:

Profile cutting, Grinding, Milling and Boring Machines, Lathes, park erosion Machines, sheet

Metal presses, Industrial Robots ,etc.

Plastic and packaging:

Mark registration ,labeling, cut to length.

Graphics:

Photo printing and developing ,Photo type setting printing presses, Film projectors and cameral, etc

Process control and Instrumentation:

Textile web control, valve controls, Material Handling systems, Assembly lines, carburetor

Adjusting, In process Gauging ,chart Recorders, servo Mechanism, Electronic gear box, profile,

precise RPM control, RPM control, RPM meter calibration



Medical Instrumens:-

Infusion pumps, x-ray and Radioactive Machinery, Blood analyzers etc.

Office Automation Equipments:

Printers, plotters, Hard and Floppy Disc, Teleprinter and Typewriters, copying Machines and

Accounting Machines

V=4*motor voltage

Rs=3*Rm(Motor resistance/phase)

Suitable for slow RPM

SWICHING LOGIC SEQUENCE

A1 A2 B1 B2

Red Green Blue Black

0 1 0 1

0 1 1 0

1 0 1 0

1 0 0 1

Q1 Q2 Q3 Q4

Half step

A1 A2 B1 B2

Red Green Blue Black

0 1 0 1

0 0 0 1

1 0 0 1

1 0 0 0

1 0 1 0

0 0 1 0

0 1 1 0

0 1 0 0

To change the direction red sequence from bottom to top

Specification:-

Permanent magnet, Bifilar wound Steps per Revolution:200

Two phase.

Step Angle:1 .8*+0r-0.1*non cumulative. No of leads-6

3kg.cm=0.1 N .m=13.90z-in



13) SERIES / PARALLEL INVERTER

(i)SERIES INVERTER

AIM : To design the series Inverter circuit and test its working.

APPRATUS REQUIRED :

Series Inverter Module, Digital Millimeter , Power Supply, Patch chords .

DESCRIPTION :

This unit consists of power circuit and firing circuit sufficient to build and study the modified series

inverter.

Firing circuit:

This part generates two pairs of pulse transformer isolated trigger two SCRs connected as series

inverter ON/OFF switch is provided

For the trigger pulses which can be used to switch ON the inverter.

Frequency of the inverter can be varied from 100hz to 1Khz approximately.

Power circuit :

This part consists of two SCRs two diodes. A center tapped inductor with tapings and capacitors

.Input supply terminals with ON/OFF

Switch and a fuse is provided .All the devices in this unit mounted on a proper heat sink, snubbed

circuit for dv/dt protection and a fuse in series with each device for short circuit protection.

All the points are brought out to front panel for inter connection. They have to be interconnected as

shown in the circuit diagram .Free wheeling diodes

Can be connected across SCRs and its effect can be observed.

Refer any standard text books for theoretical details.

Front panel details:

1.Frequency: Potentiometer to vary the inverter frequency.

2. Trigger outputs: From 100HZ to 1KHZ approximately

3.ON/OFF: Switch for trigger outputs.

4.T1 and T2: Trigger outputs.

5.Power : Mains switch for firing circuit.

6.Vdc in: Terminals for dc input-30v/2amps Max.

7.ON/OFF: Switch for dc input

8.Fuse: Fuse for dc input 2amps Glass fuse.

9.T1 and T2: SCRs TYN612.12amps/60v

10.D1 and D2: Diodes BYW51-200 4amps/200v

11.L2 L1 Lm L1 L2: 10mH-5mH-0-5mH-10mH/2 amps

12.C1 and C1: 6.8µf/100v

13.C2 and C2: 10µf/100v.



CIRCUIT DIAGRAM :

DESIGN OF SERIES INVERTER : (specimen calculation)

wr =√(1/Lc)-(R2/4L

2)

f r<=fmax = 1/(tq + π/ wr )

let tq = 10 µsec

f r = 1 k hz

wr = 20,408 r/sec

R2

< 4L/C

wr ≈ √ (1/Lc)

∴20,408 = √ (1/Lc)

let C = 10 µf

so, L = 0.240mH

R2

< 4L/C

R2

< 96

∴R < 9.6 Ω (load).



PROCEDURE:

To begin with switch on the power supply to the firing circuit.

Check that trigger pulses by varying the frequency.

Make the interconnection s of the power circuit as shown in the circuit diagram. Now connect

trigger outputs from the firing circuits to gate and cathode of SCRs T! and T2.Connect dc input

from a 30v/2amps regulated power supply. Switch on the input dc supply .Now apply trigger pulses

to the SCRs and observe voltage wave from across load vary the frequency and observe the wave

forms of the inverter frequency increases above resonant frequency of the power circuit

communication will fail. Then switch OFF the dc supply , reduce the inverter frequency and try

again if you will not get

the result check the input fuse and try again, if it fails again you have to check the fuses in series

with devices. Repeat the same with different values of L,C and load. And also observe the wave

forms with and without free diodes. The output waveform is entirely depending on load .To switch

OFF the inverter. Switch OFF the input supply first and then trigger pulses.

RESONANT FREQUENCY:

fr=1/2π √(1/LC-R*R/4L*L)

TABULAR COLUMN :

KEEPING RESISTANCE CONSTANT AT ---- Ω ,

F(Hz) Vorms (volts)

KEEPING FREQUENCY CONSTANT AT ---- Hz ,

R(Ω) Vorms (volts)



WAVEFORMS :



RESULT :

CONCLUSION :

We conclude that as and when the frequency and resistance increases the Vorms also

increases.



2) PARALLEL INVERTER

AIM : To design the series Inverter circuit and test its inverter working.

APPRATUS REQUIRED : Series Inverter Module, Digital Millimeter , Power Supply, Patch

chords .

DESCRIPTION :

This module consist of two units – (1) Firing circuit and (2) Power circuit.

1)Firing circuit :-

This unit two pairs of pulse transformer isolated trigger pulses to trigger two SCRs connected in

center tap transformer type parallel inverter. Frequency of the inverter can be varied from 75 hz to

200 hz approximately.

2)Power circuit. :-

This unit consist of two SCRs, two free wheeling diodes, commutation induction. Commutation

capacitor and a center transformer to be inter connected to make parallel inverter. All the points are

brought out to the front panel. A switch and fuse is provided for input DC supply. All the devices

are mounted on proper heat sink. Each device is protected by snubber circuit.


01.Frequency :potentiometer to vary the inverter frequency

from75Hz to 200 Hz approximately

02.ON/OFF :Switch for trigger outputs.

03.T1 & T2 :Trigger outputs.

04.Power :Mains switch for firing circuit.

05.VDC in :terminals for DC input.

06. ON :Switch for DC input.

07. TP & TN :SCR’S 10A/600V

08. DP & DN :Diodes 10A/600V

09.L :Inductance 300

10.C :6.8F/100V

11.Load :Terminals to connect the load

:Transformer center tap point which should be connected to +ve of DC supply after fuse.

13.Fuse :2A Glass fuse.

14.Output Transformer :Primary-30V-25V-0-25V-30V.

Secondary-0-30V/2Amps.



CIRCUIT DIAGRAM :

DESIGN OF PARALLEL INVERTER (specimen calculation)

L acts as current source

C is resonating element.

Lm mutual inductance of transformer and acts as a resonating inductor.

wr = √ (1/Lc)

Quality factor = Q; let Q = 4

Q = woCR ; fo = 1 khz.

Let wo = 6.280 khz

Let R = 20 Ω

∴C = 31.8 µf

& (6280) 2

= 1/LC

∴L = 0.797 mH.

Choose L = 1 mH.(should be mutual inductance of transformer).

The commutating components L & C are selected as follows:

L = Vs tq /0.425Im & C = Im tq /1.7 Vs , Im = Current at Commutation.

Vs = DC supply voltage; tq = Reverse bias time offered to SCR.



PROCEDURE :

The circuit is a typical class C parallel inverter. Assume TN to be ON and TP to be turned OFF .The

bottom of the commutating capacitor is charged to twice the supply voltage and remains at this

value until Tp is turned on .When Tp is turned on, the current flows through lower primary ,Tp and

commutating inductance L. Since voltage across c cannot raise instantaneously, the common SCR

cathode point raises approximately to 2Vdc and reverse biases TN. Thus TN turns off and C

discharges through L , the supply circuit and recharges in the reverse direction. the auto transformer

action makes C to charge making now its upper point to reach +2Vdc Volts ready to commutate Tp,

when TN is again turned on, and the cycle repeats. The major purpose of the commutating

inductance L is to limit the commutating capacitor charging current during switching.

Freewheeling diodes Dp and DN assists the inverter in handling various range of loads and the

value of C may be reduced since the capacitor now does not have to carry the reactive current. To

dampen the feedback diode currents within the half period , feedback diodes are connected to the

tapings of the transformer at 25V tapings.

Switch on the firing circuit .Observe the trigger outputs TP and TN by varying frequency

potentiometer and by operating ON/OFF switch.

Then connect input DC supply to the power circuit. Connect the trigger outputs to gate and cathode

of the SCR TP and TN. Make the interconnections as shown in circuit diagram. Connect load

between load terminals. Connect free wheeling diodes in the circuit. To begin with set input voltage

to 15V. Apply trigger pulses to SCR and observe voltage wave forms across load. Output voltage is

square wave only. Then remove the free wheeling diode connections and observe the wave forms.

Then vary the load, vary the frequency and observe the waveforms. To switch OFF the inverter

switch OFF DC input supply only. Switch OFF the trigger pulses will lead to short circuit.

Since the parallel inverter works on forced commutation ,there is a chance of commutation failure.

If the commutation fails, there is a dead short circuit in the input DC supply, which will leads to

blown off the input fuse. Please check the fuse if the commutation fails. Preferably connect the

input DC supply from the 30V/2A regulated DC power supply unit which has over current tripping

facility there by protect the DC supply unit.

If the commutation fails, switch off the DC supply first and then trigger outputs.

Check the connections again.

TABULAR COLUMN :

KEEPING RESISTANCE CONSTANT AT ---- Ω ,

F(Hz) Vorms (volts)

KEEPING FREQUENCY CONSTANT AT ---- Hz ,

R(Ω) Vorms (volts)



WAVEFORMS :

RESULT :

CONCLUSION :

We conclude that as and when the frequency and resistance increases the Vorms also

increases.



INTRODUCTION OF ORCAD CIRCUIT DESIGN & SIMULATION

Step 1: Software opens by clicking an option “CAPTURE LITE” in the start menu.

Step 2: To start with a PSpice project:

• Go to “File” menu. Select “New Project” option.

• Choose “analog or mixed A/D” option and specify the project name and its location and

click Ok

Step 3: Once the step (2) is completed the following window appears. Choose “Create a blank

project” option.



Step 4: Create the circuit by placing all its parts using “Part” option from “Place” menu. In this

way a complete electrical circuit can be formed.



Step 5: After completing the circuit, make the simulation profile using “New Simulation Profile”

command from “PSpice” menu.

Step 6: Go to “Edit Simulation Profile” in “PSpice” menu, simulation settings window will open.

Go to “Analysis” and set the simulation parameters as shown below.



Step 7: Place the markers (voltage or current) near the required component on the circuit by using

command “MARKERS” from “PSpice” menu.

Step 8: Run the simulation by using command “RUN” from “PSpice” menu.



Step 9: And the results will be plotted.



CONVERTER CIRCUITS USING ORCAD PSPICE

1. Controlled HWR and FWR using RC triggering circuit 1. a) Half controlled rectifier using RC triggering circuit.

Circuit Diagram

V2

FREQ = 50VAMPL = 30vVOFF = 0

R1

100

D1

D1N914

R3

1k

R2

100

2

1

X1

2N1595

C1

1uF1

2

D2

D1N914

0

Output Waveform:



1. b) Fully controlled rectifier using RC triggering circuit

Circuit Diagram

D1

D1N914

D5

D1N914

R2

1k

D4

D1N914 C1

0.47uf1

2

D3

D1N914V4

FREQ = 50VAMPL = 10vVOFF = 0

X1

2N1595R3

3.3k

2

1

R1

100

0

D2

D1N914

Output Waveform:



2. AC voltage controller using TRIAC – DIAC combination.

Circuit Diagram

C148uf

1

2

D2D1N914

V1

FREQ = 50VAMPL = 200v

VOFF = 0

X1

2N5444

0

R2

1k

D1

D1N914

R1

50

21

Output Waveform:



4. Voltage (Impulse) commutated chopper

Circuit Diagram

D2

D1N914

L1

10mH

1 2

V2

TD = talpha+1/(2*f )

TF = 0.1uPW = 0.5/f PER = 1/f

V1 = 0

TR = 0.1u

V2 = 5

D1

D1N914

V1

TD = talpha

TF = 0.1uPW = 0.5/f PER = 1/f

V1 = 0

TR = 0.1u

V2 = 5

0

C1

1uf1

2

X1

2N1595

X2

2N1595

V3

10Vdc

PARAM ET ERS:talpha = alpha/(360*f )alpha = 60f = 50

R2

100

2

1

L2

10mH

1 2



Output Waveform:



5. Series inverter.

Circuit Diagram

D2

D1N914

C1

10uF1

2

V2

TD = talpha+1/(2*f )

TF = 0.1uPW = 0.5/f PER = 1/f

V1 = 0

TR = 0.1u

V2 = 5

0

D1

D1N914V1

40Vdc

C2

10uF1

2

X1

2N1595

L1

10mH

1

2 R3

50

V3

TD = talpha

TF = 0.1uPW = 0.5/f PER = 1/f

V1 = 0

TR = 0.1u

V2 = 5

X2

2N1595

L2

10mH

1

2

PARAM ET ERS:talpha = alpha/(360*f )alpha = 60f = 75



Output Waveform:



MODEL QUESTION BANK OF LABORATORY

Expt. No. QUESTION

1

Conduct a suitable experiment to determine the V-I Characteristics of “Unidirectional

four layer switch” for different gate currents. Determine break down voltage and holding

current for two cases.

2

Conduct a suitable experiment to determine the V-I Characteristics of “Bi-directional four

layer switch”. Determine break down voltage and holding current in 1st and 3

rd quadrants

and comment on its sensitivity.

3

Conduct a suitable experiment on MOSFET to verify its on – state resistance and gate

threshold voltage. Plot the transfer characteristics and output static characteristics.

4

Conduct a suitable experiment to determine the V-I Characteristics o IGBT. Comment on

its switching characteristics.

5

Conduct a suitable experiment to control Half Wave Rectifier using RC firing circuit and

plot a graph of load voltage versus firing angle and various waveforms.

6 Conduct a suitable experiment to control Full Wave Rectifier using RC firing circuit and

plot a graph of load voltage versus firing angle and various waveforms

7 Design a synchronized UJT Relaxation Oscillator circuit to turn ON the SCR and hence

plot various waveforms.

8

Design a synchronized UJT Relaxation Oscillator circuit for controlling Half Wave

Rectifier and hence plot a graph of load voltage versus firing angle & various waveforms.

9

Design a synchronized UJT Relaxation Oscillator circuit for controlling Full wave

rectifier and hence plot a graph load voltage versus firing angle & various waveforms.

10

Conduct a suitable experiment on LC commutation circuit to prove that conduction period

of SCR depends on commutating elements (R, L and C ). OR Auxiliary Commutation

11

Conduct a suitable experiment to control the speed of an AC motor/Brightness of a lamp

using TRIAC–DIAC combination. Draw the graph of firing angle Vs speed/Vorms

12

Conduct a suitable experiment on half controlled/fully controlled bridge rectifier with

resistive load /R-L load. Plot DC voltage Vs. delay angle graph.

13

Conduct a suitable experiment to experiment to control the speed of separately excited

DC motor and plot a graph of speed versus firing angle and Vodc Vs firing angle.

14

Conduct a suitable experiment on Chopper to convert constant DC voltage to variable DC

voltage with a duty cycle of ___________ check the result with

theoretical value.

15

Conduct a suitable experiment to verify the operating principle of a single phase

Series/Parallel inverter and hence plot various waveforms of the inverter



VIVA QUESTIONS

1. What is SCR ?

2. What is TRIAC ?

3. What is DIAC?

4. What is MOSFET ?

5. What is IGBT ?

6. What is meant by commutation ?

7. What is the difference between TRIAC and DIAC ?

8. What is the difference between MOSFET and IGBT ?

9. What is the difference between UJT and BJT ?

10. How di/dt and dv/dt protection is provided for power transistors ?

11. What is the use of isolator ?

12. What is the difference between n-channel and p-channel MOSFET ?

13. What do you understand by threshold and pinch- off voltages ?

14. What is the importance of holding current ?

15. What do you understand by latching current ?

16. What is pulse transformer ?

17. What is the need of a transformer in circuits ?

18. Name few applications of MOSFETs and IGBTs .

19. List the factors that affect the turn ON turn OFF times of a power BJT .

20. Name the terminals of MOSFET .

21. What do understand by thyristor ?

22. What is snubber circuit ?

23. What is the affect of gate current on break over voltage in SCR ?

24. State the conditions to be satisfied for proper turn off of an SCR.

25. What are the different methods of commutation of SCRs ?

26. What is line commutation ?

27. What is impulse commutation ?

28. What is self commutation ?

29. How to turn off an SCR properly ?

30. What is auxiliary commutation ?

31. What is an AC voltage controller ?

32. List the different types of ACVC.

33. What are the applications of ACVC ?

34. What is controlled rectifier ?

35. Give the classifications of controlled rectifier circuits .

36. List the applications of rectifiers .

37. What is the difference between uncontrolled and controlled rectifier ?

38. What is chopper ?

39. What are the methods of chopper control ?

40. How will you classify choppers ?

41. What is the function of an inverter ?

42. List different types of inverters.

43. What is the difference between a converter and a inverter ?

44. What are the applications of inverters ?

45. What are the advantages and disadvantages of current source inverters ?

46. What is the difference between series and parallel inverter ?

47. What is the use of free wheeling diode ?



48. List the different methods of voltage control adopted in inverters .

49. What are the different types of thyristor firing circuits ?

50. What is dimmer stat ?

51. What is power electronics ?

52. What are the merits of power electronics ?

53. What are the demerits of power electronics ?

54. What are the applications of power electronics ?

55. What are the important parameters of SCR ?

56. What are the important parameters of MOSFET ?

57. What are the important parameters of IGBT ?

58. What are the important parameters of TRIAC ?

59. What are the important parameters of DIAC ?

60. What are the important parameters of power BJT ?

Note: Instruction Classes will be taken for the students to introduce and explain the

laboratory experiments and use of equipments.

BIBLIOGRAPHY

1. Manual by FRAX ELECTRO SYSTEMS

2. Power electronics by Mohamed Rashid.

3. Power electronics by Bhimra

4. Power electronics by Nattarasu.