1. verification of ohms law · web viewverification of kvl and kcl transient response of series rl...

B.Tech. I Year Syllabus

BASIC ELECTRICAL ENGINEERING LAB

B.Tech. I Year I Sem. L0

T0

P C2 1

Course Objectives:To analyze a given network by applying various electrical laws and network theorems To know the response of electrical circuits for different excitationsTo calculate, measure and know the relation between basic electrical parameters.To analyze the performance characteristics of DC and AC electrical machines

Course Outcomes:Get an exposure to basic electrical laws.Understand the response of different types of electrical circuits to different excitations.Understand the measurement, calculation and relation between the basic electrical parametersUnderstand the basic characteristics of transformers and electrical machines.

List of experiments/demonstrations:1. Verification of Ohms Law

2. Verification of KVL and KCL

3. Transient Response of Series RL and RC circuits using DC excitation

4. Transient Response of RLC Series circuit using DC excitation

5. Resonance in series RLC circuit

6. Calculations and Verification of Impedance and Current of RL, RC and RLC series circuits7. Measurement of Voltage, Current and Real Power in primary and Secondary Circuits of a Single Phase

Transformer

8. Load Test on Single Phase Transformer (Calculate Efficiency and Regulation)

9. Three Phase Transformer: Verification of Relationship between Voltages and Currents (Star-Delta, Delta-Delta, Delta-star, Star-Star)

10. Measurement of Active and Reactive Power in a balanced Three-phase circuit

11. Performance Characteristics of a Separately/Self Excited DC Shunt/Compound Motor

12. Torque-Speed Characteristics of a Separately/Self Excited DC Shunt/Compound Motor13. Performance Characteristics of a Three-phase Induction Motor

14. Torque-Speed Characteristics of a Three-phase Induction Motor

15. No-Load Characteristics of a Three-phase Alternator

1. VERIFICATION OF OHMS LAW

1.1 OBJECTIVE To verify The Ohms Law

1.2 RESOURCES

S.No. Name of the equipment Type Range Qty01 Voltmeters DC Digital (0-20)V 0102 Ammeters DC Digital (0-2)A 0103 Resisters ----- ---04 DC Power Supply source ------ 15 Volts DC / 2 amp ----

1.3 CIRCUIT DIAGRAM

1.4 PROCEDURE1. Give the connections as per the circuit diagram.

2. Set a particular value in DC Power source.

3. Note down the corresponding ammeter reading

4. Repeat the same for different Voltage and verify the ohm’s law V=IR

1.5 TABULAR COLUMNSl.

No.Voltage

VCurrent

A01020304

1.6 GRAPH

1.7 PRE LAB QUESTIONS: 1. What is current? 2. What is voltage?

3. Define charge. 4. Define power. 5. What is the resistance? 6. What is ohm’s law? 1.8POST LAB QUESTIONS: 1. What do you mean by junction? 2. What is the colour coding of resistors? 3. What are the precautions to be taken while doing the experiment? 4. What is the range of ammeters and voltmeters you used in this experiment? 5. What are the limitations of ohm’s law? 6. What is the condition of ohm’s law?

1.9 RESULT: Hence Ohms Law is Verified.

2. Verification of KVL and KCL

2.1 AIM :

To verify The KVL & KCL For The Given Circuits.

2.2 APPARATUS REQUIRED :

Sl.No. Apparatus Type Range Quantity01 Voltmeters DC Digital (0-20)V 0302 Ammeters DC Digital (0-2)A 0303 Resisters --- ---04 DC Power Supply source ----- 15 Volts DC / 1 amp ------05 Connecting Wires ----- Required

2.3 CIRCUIT DIAGRAMCIRCUIT DIAGRAM FOR KCL :

CIRCUIT DIAGRAM FOR KVL :

2.4 PROCEDURE FOR KCL:

1. Give the connections as per the circuit diagram.2. Set a particular value in DC Power source.3. Note down the corresponding ammeter reading4. Repeat the same for different voltages

PROCEDURE FOR KVL:

1. Give the connections as per the circuit diagram.2. Set a particular value in DC Power source.3. Note all the voltage reading4. Repeat the same for different voltages

2.5 OBSERVATION TABLES :

KCL :

Sl. Voltage Current I1 = I2 + I3

No. E I1 I2 I3

Volts A A A A01020304

KVL :

Sl.Voltage E Voltage KVL

No. V1 V2 E1 = V1 + V2

(E1) Volts V V

01020304

2.6PRE LAB VIVA QUESTIONS: 1. What is current? 2. What is voltage? 3. What is resistance? 4. What is ohm’s law? 5. What is KCL and KVL? 2.7 POST LAB VIVA QUESTIONS: 1. What do you mean by junction? 2. What directions should be assumed for KCL? 3. What are the positive and negative signs in KVL? 4. What is the colour coding of resistors? 5. What are the precautions to be taken while doing the experiment? 6. What is the range of ammeters and voltmeters you used in this experiment?

2.8 RESULT: Hence KCL and KVL are verified theoretically and practically.

3. TRANSIENT RESPONSE OF SERIES RL AND RC CIRCUITS USING DC EXCITATION

3.1 AIM :

Study the transient response of a series RC circuit and understand the time constant concept with DC Power Supply.


Sl.No. Apparatus Range Quantity01 Resistors R1, R2 and R3 in 03

Kilo ohms02 Inductors L in milli Henrys 0103 Capacitors C in micro farad 0104 DC Power Supply source 15 Volts DC / 1 amp ------05 Connecting Wires ----- Required06 Digital Storage Oscilloscope (CADO 30MHZ 01

801)

3.3 CIRCUIT DIAGRAM FOR RC & RL CIRCUIT :

RC & RL CIRCUIT

3.4 PROCEDURE: (For RC circuit)

1. Make sure that the toggle switch connected across the DC Supply is in downward position.2. Connect +5V DC Power Supply to the input of RC Circuit i.e., connect +5V terminal to

terminal 1 and Gnd terminal to terminal 2.3. Connect the mains cord to the Trainer and switch ‘On’ the mains supply.4. Connect terminal 3 with resistance R1 (terminal 4).5. Now switch ‘On’ the power switch of the trainer.

6. Connect DSO across capacitor i.e. across terminal 7 and terminal 8. Keep DSO at 10 seconds or more Time Base.

7. Switch the toggle switch in upward direction so that DC Supply will connect to the RC circuit.

8. Observe the transient response (exponentially rising) on DSO till the steady state (+5V DC level) is achieved i.e. for 50 seconds (for case R=10 K and C= 1000 μF).

9. Now switch the toggle switch in downward direction so that resistor, R will short with capacitor, C.

10. Now observe the response (exponentially decaying) till it reaches reference level of DSO. Now immediately press RUN/STOP Switch of DSO to hold the response shown on the DSO screen.

11. Repeat the procedure for the different resistors provided, observe and analyze the result.

Calculations: (RC circuit)

1. Theoretically,

Time Constant, TC = R C = ……………..

where,

R1 = 10 K, C = 1000 μF.

R2 = 20 K, C = 1000 μF.

R3 = 3.3 K, C = 1000 μF.

Practically (on DSO screen),

In the charging circuit, Time Constant is the time by which the capacitor attains the 63.2% of steady state voltage or final value (in our case, +5 V).

Time Constant or Time required to rise to 63.2% of 5 V (i.e. 3.16 V) =…………In the discharging circuit, Time Constant is time by which the capacitor discharges to 36.8% of its initial steady state voltage (in our case, +5 V).

Time Constant or Time required to decay to 36.8% of 5V (i.e. 1.84 V) = ………….

2. Similarly, 2TC is the time required to achieve 86.5% of final or initial value of voltage (i.e. 4.3V).

Practically, 2TC = ……….Theoretically, 2TC =……...

3. After 5TC, the voltage reaches it’s final value which is also called steady state response (i.e. 5V).

Practically, 5TC = ……….Theoretically, 5TC =……...

PROCEDURE: (For RL circuit)

1. Make sure that the toggle switch connected across the DC Supply is in downward position.

2. Connect +5 V DC Power Supply to the input of RL Circuit i.e. connect +5 V terminal to terminal 1 and Gnd terminal to terminal 2.

3. Connect the mains cord to the Trainer and switch ‘On’ the mains supply.4. Now switch ‘On’ the power switch of the trainer.5. Connect DSO across inductor i.e. across terminal 7 and terminal 8. Keep DSO at 200 μs or 500 μs Time Base .6. Observe the transient response switching the toggle switch in upward and downward direction continuously. Now

immediately press RUN/STOP Switch of DSO to hold the response shown on the DSO screen.7. Select the waveform with appropriate peak and observe the time constant on DSO.

Calculations:

4. Theoretically,

Time Constant, TC = R C = ……………..

where,

L = 800 mH, R1 = 1 K

L = 800 mH, R2 = 2 K

L = 800 mH, R3 = 3.3 K

Practically (on DSO screen),

In the charging circuit, One Time Constant is the time by which the inductor attains the 36.8% of maximum voltage (in our case, +5 V).

Time Constant or Time required to decay to 36.8% of 5 V (i.e. 1.84 V) = ………….

3.5 PRE LAB QUESTIONS

1) Define Transient and classify

2) Deduce the time constant for simple RL series circuit.

3) Deduce the time constant for simple RC series circuit.

4) How will you design the values of L & C in a transient circuit?

3.6 POST LAB QUESTIONS

1) Why it is necessary to discharge the capacitor every time you want to record another transient voltage across the capacitor?

2) If the capacitor remains charged, what would you expect to see across the capacitor when you re-close the switch to try to record

another transient?

3) Give the expression for energy stored in the capacitor?

4) Draw the discharge of capacitor voltage with time in RC circuit?

5) What do you understand from the value of time constants (RL, RC)?

3.7 RESULT: Transients analysis of RL series circuit and RC series are performed and time constant values are calculated for RL and RC series circuits with DC supply.

4. TRANSIENT RESPONSE OF SERIES RLC CIRCUIT USING DC EXCITATION

4.1 AIM:Study the transient response of a series RLC circuit and understand the time constant concept with

DC Power Supply.


Sl.No. Apparatus Range Quantity01 Resisters R1, R2 and R3 in 03

Kilo ohms02 Inductors L in milli Henrys 0303 Capacitors C in micro farad 0104 DC Power Supply source 15 Volts DC / 1 amp ------05 Connecting Wires ----- Required06 Digital Storage Oscilloscope (CADO 30MHZ 01

801)

4.3 CIRCUIT DIAGRAM FOR RLC CIRCUIT :

RLC CIRCUIT

4.4 PROCEDURE: (For RLC circuit)

1. Connect square wave (TTL) to the input of RLC circuit i.e. connect TTL signal terminal to terminal 1 and Gnd terminal to terminal 2. Square Wave (TTL) is just like manual switching as it automatically switches on and off.

2. Connect the mains cord to the Trainer and switch ‘On’ the mains supply.3. Connect terminal 3 with resistance R1 (terminal 4).4. Now switch ‘On’ the power switch of the trainer.5. Connect DSO across capacitor i.e. across terminal 7 and terminal 8. Keep DSO at 10 seconds or more Time Base.6. Switch the toggle switch in upward direction so that DC Supply will connect to the RC circuit.

7. Observe the transient response (exponentially rising) on DSO till the steady state (+5V DC level) is achieved i.e. for 50 seconds.

8. Now switch the toggle switch in downward direction so that resistor, R will short with capacitor, C.

9. Now observe the response (exponentially decaying) till it reaches reference level of DSO. Now immediately press RUN/STOP Switch of DSO to hold the response shown on the DSO screen.

10. Repeat the procedure for the different resistors provided, observe and analyze the result.

Follow the same procedure for different caseswhenC=1000 pF,

= 63 Ω approx.L1 = 10 mH, RL1

L2 = 15 mH, RL2 = 97 Ω approx.L3 = 20 mH, RL3 = 133 Ω approx.


1) Define Transient and classify

2) Deduce the time constant for simple RL series circuit.

3) Deduce the time constant for simple RC series circuit.

4) How will you design the values of L & C in a transient circuit?

4.6 POST LAB QUESTIONS

1) Why it is necessary to discharge the capacitor every time you want to record another transient voltage across the capacitor?

2) If the capacitor remains charged, what would you expect to see across the capacitor when you re-close the switch to try to record

another transient?

3) Give the expression for energy stored in the capacitor?

4) Draw the discharge of capacitor voltage with time in RC circuit?

5) What do you understand from the value of time constants (RL, RC)?

4.7 RESULT:Transients analysis of RLC is verified.

5. RESONANCE IN SERIES AND PARALLEL RLC CIRCUITS

5.1AIM:

To determine the resonant frequency fo, Bandwidth and quality factor Q, of the given series and parallel RLC circuits.

5.2 APPARATUS REQUIRED:

Sl.No. Apparatus Range Quantity01 Resistor 0102 Inductor 0103 Capacitor 0104 Function Generator ------05 Connecting Wires ----- Required

5.3 CIRCUIT DIAGRAM:

SERIES RESONANCE

5.4 PROCEDURE:

Resonance in series RLC circuits:

1. Set the signal generator in sine wave mode and the output voltage to 20V peak to peak.

2. Connect the circuit as per fig and vary the frequency of the input signal in steps and note down the corresponding current through the circuit and tabulate the readings.3.Reduce the frequency to zero and disconnect the circuit and plot the graph by relating dependent and

independent variables.

5.5 PRECAUTIONS:

1. Keep the output voltage of the signal generator in zero volt position.2. Set the ammeter pointer at zero position.3. Take the readings without parallax error.4. Avoid loose connections5.6 Formulas:

5.7TABULAR COLUMN:

SERIES RESONANCESl.no Frequency, f (Hz) Current, I(mA)

OBSERVATIONS:

SERIES RESONANTSl.No PARAMETER CIRCUIT

Theoretical PracticalValues Values

1 Resonant Frequency, (fo)

2 Band width

3 Quality factor

5.8 PRE LAB QUESTIONS 1. What is resonance.?2. What is the condition for resonance?3. What are the applications of resonance?POST LAB QUESTION

1. What do understood by conducting this test.2. Is resonance condition is justified in this test.

5.9 RESULT:

Resonance of series circuit is verified and resonance frequency, band width and quality factor are calculated.

6. VERIFICATION OF IMPEDANCE AND CURRENT OF RL, RC AND RLC SERIES CIRCUITS

6.1 AIM: To verify the Impedance and Current of RL, RC And RLC Series Circuits


Sl.No. Apparatus Range Quantity01 Resisters 25 ohms 0102 Inductors 110 milli Henrys 0103 Capacitors 160 micro farad 0104 AC Power Supply source 30 Volts AC / 1 amp ------05 Connecting Wires ----- Required

6.3 CIRCUIT DIAGRAM FOR RL SERIES CIRCUIT :

Fig: 1 RL SERIES CIRCUIT

CIRCUIT DIAGRAM FOR RC SERIES CIRCUIT :

Fig: 2 RC SERIES CIRCUIT

CIRCUIT DIAGRAM FOR RLC SERIES CIRCUIT :

Fig: 3 RLC SERIES CIRCUIT

6.4 PROCEDURE:

A) RL SERIES CIRCUIT:

1. Connect the mains cord to the Trainer and switch ‘On’ the mains supply.2. Make the connections as per fig:1 as shown in above.3. Apply some Voltage using Variac up to 30 Volts in steps wise.4. Note down all parameters (Voltage and Current)5. Tabulate the readings.6. Calculate the Impedance (Z) and Current.

B) RC SERIES CIRCUIT:


C) RLC SERIES CIRCUIT:


OBSERVATION TABLE:

V (Volts) I (Amps) Z (Ohms)RL CircuitRC CircuitRLC Circuit

SAMPLE CALCULATIONS: (RL, RC & RLC Series Circuit)

6.5.PRE LAB QUESTION

1. What is reactance?2. What is the need of reactance?3. Define impedance.4. What is the phase angle between v & I in rl, rc & rlc circuits?

POST LAB QUESTIONS1. IS the angle same for theoretical and practical?

6.6 RESULT:Impedance for RL,RC and RLC circuits are calculated.

7. Measurement of voltage, current and real power in primary and secondary circuits of a single phase trans former

7.1 Aim:

To measure the voltage, current and real power in the primary and secondary of the single phase transformer7.2 Apparatus required:

S. No. Equipments Type & Specifications Quantity

1 Transformer 1-Φ ,500VA 1 No.

2 A.C. Ammeter Digital (0 – 20) A 1 No.

3 A.C Voltmeter Digital (0–500)V 2 No’s5 U.P.F Wattmeter Dynamometer Type, 1 No.

250V/5A

6. Auto Transformer 1-ϕ,6 Amps,230 Volts 1 No.7 Connecting wires --- Required

7.3 Name plate details:

Power = VA

L.V Side Voltage = Volts

H.V Side Voltage = Volts

L.V Side current = Amps

H.V Side current = Amps

Frequency = Hz

7.4 Circuit diagram:

Observations for Load Test; (purely resistive)

V1 = 230 V (Constant)

S.No Primary Secondary % % Reg.V1 (V) I1 (A) W1(KW) V2(V) I2(A) W2(KW)

7.5 Precautions:

1 Avoid loose connections.2 Don’t touch the circuit connections while power is on.3 Take the meter readings without parallax error.4 Voltage is to be varied gradually till rated current flows.5 Ensure that the setting of the variac is at zero output voltage during starting

5. What is the necessity of the load test for a transformer?7.6PRE LAB QUESTIONS:

2. Why is the core of a transformer laminated?

3. What is meant by regulation?

4. Define the term transformation ratio?

5. What are the components of no load current?

6. What are the parameters of the equivalent circuit?

7. How are the parameters referred to the HV or LV side? Explain with an example

8. What is the basic principle of operation of a single phase transformer?

9. What are the losses in a transformer?

10. Why the efficiency of transformer is higher than the rotating machines?

POST LAB QUESTIONS:

1. For a good transformer regulation should be low or high.

2. What information you will get by conducting O.C & S.C tests?

3. What do you mean by predetermination of efficiency and regulation of a transformer?

4. What happens if the primary of the transformer is excited by a D.C source?

5. What is the condition for maximum efficiency?

Result : Voltages, current and real power of primary and secondary side are calculated.

8. Load Test on Single Phase Transformer8.1 Aim:

To determine the efficiency and voltage regulation of a single Phase Transformer by direct applying of different loads on secondary side of transformer.

8.2 Apparatus required:

S. No. Equipments Type & Specifications Quantity

1 Transformer 1-Φ ,500VA 1 No.

2 A.C. Ammeter Digital (0 – 20) A 1 No.

3 A.C Voltmeter Digital (0–500)V 2 No’s5 U.P.F Wattmeter Dynamometer Type, 1 No.

250V/5A

6. Auto Transformer 1-ϕ,6 Amps,230 Volts 1 No.7 Connecting wires --- Required

8.3 Name plate details:

Power = VA

L.V Side Voltage = Volts

H.V Side Voltage = Volts

L.V Side current = Amps

H.V Side current = Amps

Frequency = Hz

8.4 Circuit diagram:

Observations for Load Test; (purely resistive)

V1 = 230 V (Constant)

S.No Primary Secondary % % Reg.V1 (V) I1 (A) W1(KW) V2(V) I2(A) W2(KW)

% Efficiency η = Output powerX 100Input power

% Regulation = (E0 – V) /V X 100 V

Model graphs:

Efficiency Vs Output Power Regulation Vs Power factor

8.5 Precautions:

1 Avoid loose connections.2 Don’t touch the circuit connections while power is on.3 Take the meter readings without parallax error.4 Voltage is to be varied gradually till rated current flows.5 Ensure that the setting of the variac is at zero output voltage during starting

5. What is the necessity of the load test for a transformer?8.6 PRE LAB QUESTIONS:

2. Why is the core of a transformer laminated?

3. What is meant by regulation?

4. Define the term transformation ratio?

5. What are the components of no load current?

6. What are the parameters of the equivalent circuit?

7. How are the parameters referred to the HV or LV side? Explain with an example

11. What is the basic principle of operation of a single phase transformer?

12. What are the losses in a transformer?

13. Why the efficiency of transformer is higher than the rotating machines?

POST LAB QUESTIONS:

6. For a good transformer regulation should be low or high.

7. What information you will get by conducting O.C & S.C tests?

8. What do you mean by predetermination of efficiency and regulation of a transformer?

9. What happens if the primary of the transformer is excited by a D.C source?

10. What is the condition for maximum efficiency?

8.7 Result : Efficiency and regulation of transformer are calculated.

9.Three Phase Transformer: Verification of Relationship between Voltages and Currents (Star-Delta, Delta-Delta, Delta-star, Star-Star)

9.1 AIM: To verify the Relationship between Voltages and Currents of 3 ph transformer (Star-Delta, Delta-Delta, Delta-star, Star-Star)


Sl.No Equipment name quantity01 Digital voltmeter (0-500VAC) 0202 Digital ammeter (0-20 AAC) 0203 3 Ph auto transformer 0104 3 Ph transformer 0105 Balanced resistive load 0106 Connecting wires. As Required

9.3 CIRCUIT DIAGRAM: (For STAR and STAR Configuration)

CIRCUIT DIAGRAM: (For DELTA and DELTA Configuration)

CIRCUIT DIAGRAM: (For DELTA and STAR Configuration)

Fig 3

CIRCUIT DIAGRAM: (For STAR and DELTA Configuration)

9.4 PROCEDURE: (For Balanced connected Loads)

1. Make the connections as per the circuit diagram.( fig 1)2. Connect the supply to the STAR connected load through all meters as per the circuit diagram.3. Switch ON the MCB.4. Apply Voltage using Three Phase dimmerstat up to 400Volts.5. Note down the Readings of voltmeter, ammeter.6. Switch OFF the STAR Connected load.7. Tabulate the readings.8. Repeat the same procedure for (fig 2,3,4) remaining configurations.

9.5 OBSERVATIONS:

PRIMARY SECONDARY

Transformer VOLTAGE CURRENT VOLTAGE CURRENTConfiguration (L-L) (L-L)

STAR/STARDELTA/DELTADELTA/STARSTAR/DELTA

9.6 CALCULATIONS:

9.7.PRELAB QUESTIONS

1. What are the three phase connections.2. Tell me need of three phase transformer.3. What are relations of line and phase voltage, current in star system.4. What are relations of line and phase voltage, current in delta system.

POST LAB QUESTIONS.1. What is the turns ratio.2. Which connection is used for high voltage applications.3. Which connection is used for low voltage applications4. Which connection is used for high current applications

5. Which connection is used for low current applications6.

9.8RESULT: relationship between voltage and current for different three phase transformer connections are verified.

9. MEASUREMENT OF 3-PHASE ACTIVE AND REACTIVE POWER FOR BALANCED LOAD

10.1AIM: To measure the Active and Reactive power for STAR connected balanced loads.

10.2APPARATUS REQUIRED:

Sl.No Equipment name quantity01 Digital voltmeter (0-500Volts AC) 0102 Digital ammeter (0-10Amps AC) 0103 Analog wattmeter (0-500V, 5Amps) 0204 R-Load bank. (STAR Connected) 0105 Experiment setup. 0106 Connecting wires. As Required

10.3 CIRCUIT DIAGRAM: (For STAR connected Loads)

10.4 PROCEDURE: (For Balanced connected Loads)

1. Make the connections as per the circuit diagram.2. Connect the supply to the STAR connected load through all meters as per the circuit diagram.3. Switch ON the MCB.4. Apply Voltage using Three Phase dimmer stat up to 400Volts.5. Note down the Readings of voltmeter, ammeter, and wattmeter.6. Switch OFF the STAR Connected load.

10.5 OBSERVATIONS:

S.NO VOLTAGE CURRENT Total Active Power (Reactive Power)(W1+W2) √3 (W1-W2)

1.2.3.

10.6 CALCULATIONS:

W1 W2 TAN

3W1 W2 1

3 W W TAN

1 2

W1 W2

10.7 PRECAUTIONS:

1. Avoid loose/ wrong connections.2. Switch off the supply after doing the experiment.


1. What is active power and reactive power.

2. What is the need of reactive power.

3. How will measure the reactive power.

POST LAB QUESTIONS

1. Draw the power triangle.

2. Is any difference in reactive power if capacitive and inductive load is connected individually?

3. How can we use reactive power in power system applications?

RESULT: Active and Reactive powers are calculated.

11. PERFORMANCE CHARACTERISTICS OF A SEPARATELY EXCITED DC MOTOR

11.1 Aim: To determine the efficiency of a DC shunt motor by conducting brake test.

11.2 Apparatus:

Voltmeter 0 – 300V (MC) 1 NoAmmeter 0 – 30A (MC) 1 NoAmmeter 0 – 1A (MC) 1 NoTachometer 1 No

11.3 Circuit diagram

11.4 Procedure:1. Give the connections as per the circuit diagram.

2. Start the motor using the starter.

3. Increase the load by tightening the brake band and note the observations of the ammeter,

voltmeter, tachometer and the applied loads S1and S2 till rated current is attained. Take at least six readings

4. Unload the motor by slackening the brake band.

5. Switch off the supply to the motor by opening the DPST switch. Find the radius of the Brake drum

11.5 Precaution:

Before starting the experiment pour some water into the brake drum and also while doing the experiment.

Stay away from the brake drum when switching off the motor.

11.6 Readings and calculations:

Sno. V IL N S1 S2 W=S1-S2 T= 9.81 Output= Input η =

(Volt) (Amp (rpm) (Kg) (Kg) (Kg) W r 2πNT/60 VIL output/) (Nm) (watts) (Watts) Input

(%)

(“r” is the radius of the brake drum)

Expected graph:

11.7 PRE LAB QUESTIONS: 1. What is a motor? 2. What is the principle of operation of motor?3. What are the different types of motors? 4. What is residual magnetism? 5. What is the Flemings left hand rule? 6. What is the EMF equation of motor? POST LAB QUESTIONS: 1. What is the rating of motor used?2. What is the stator rating used? 3. What is meant by starter? 4. What type of starter is used in your experiment? 5. How you can vary the speed of generator?

11.8 Results: performance curves of dc separately excited dc motor are drawn by conducting brake test.

12. TORQUE – SPEED CHARACTERISTICS OF A DC COMPOUND MOTOR

12.1 Aim: To determine the efficiency of a DC compound motor by conducting brake test.

12.2 Apparatus:

Voltmeter 0 – 300V (MC) 1 NoAmmeter 0 – 30A (MC) 1 NoAmmeter 0 – 1A (MC) 1 NoTachometer Digital 1 No

12.3 Circuit Diagram:

12.4 Procedure:1. Give the connections as per the circuit diagram.2. Start the motor with the starter3. Increase the load by tightening the brake band and note the observations of the ammeter, voltmeter,

tachometer and the applied loads S1 and S2 till rated current is attained. Take at least six readings.4. Unload the motor by slackening the brake band.5. Switch off the supply to the motor by opening the DPST switch. Find the radius of the Brake drum.

12.5 Precaution

Before starting the experiment pour some water into the brake drum and also while doing the experiment.

Stay away from the brake drum when switching off the motor.

12.6 Readings and calculations:

Sno V IL N S1 S2 W=S1- T= Output= Input N=. Volts Amps rpm Kg Kg S2 9.81Wr 2πNT/6 VIL output/Inp

Kg Nm 0 Watts ut %watts

12.7 Expected graphs:

12.8 PRE LAB QUESTIONS:

1. Differentiate between cumulative compound and differential compound motors

2. The differentially compounded motor has a tendency to start in the opposite direction, why?

3. Mention the applications of DC compound motor

4. What are the advantages of a compound motor?

What happen, if the field circuit of a loaded cumulative compound motor is suddenly opened?

12.9 POST LAB QUESTIONS:

1. Explain the difference between long shunt and short shunt compounding?

2. What are the uses of different types of compound motors?

3. How do you reverse the direction of motor?

4. What is flat compounding?

5. In a dc Machine, windage losses vary with speed in the proportion of...

6. Brake test on DC motors is usually restricted to ......HP motors

7. How do you minimize iron losses in a dc machine?

12.10 Results: torque speed curve of dc compound motor is drawn by conducting brake test.

13. PERFORMANCE CHARACTERISTICS OF A 3- INDUCTION MOTOR

13.1 AIM:

To determine the efficiency of 3- induction motor by performing load test.

To obtain the performance curves for the same.


Sl.Equipment Type Range Quantity

No.

1 Voltmeter MI (0-600)V 1 no

2 Ammeter MI (0-10)A 1 no

10A/600V UPF 1 no3 Wattmeter Electro dynamo meter type

10A/600V LPF 1 no

4 Tachometer Digital 0-9999 RPM 1 no

5 Connecting Wires ***** ***** Required


13.4 PROCEDURE:

1. Connections are made as per the circuit diagram.

2. Ensure that the 3- variac is kept at minimum output voltage position and belt is freely suspended.

3. Switch ON the supply. Increase the variac output voltage gradually until rated voltage is

observed in voltmeter. Note that the induction motor takes large current initially, so, keep an

eye on the ammeter such that the starting current current should not exceed 7 Amp.

4. By the time speed gains rated value, note down the readings of voltmeter, ammeter, and wattmeter at no-load.

5. Now the increase the mechanical load by tightening the belt around the brake drum gradually in steps.

6. Note down the various meters readings at different values of load till the ammeter shows the rated current.

7. Reduce the load on the motor finally, and switch OFF the supply.

13.5 MODEL CALCULATIONS:

Input power drawn by the motor W = (W1 + W2) watts

Shaft Torque, Tsh = 9.81 (S1 ~ S2) R N-m RRadius of drum in mts.

2N T

sh

Output power in watts = watts60

% efficiency output power in watts x 100Input power in watts

Ns N 120 x f% slip x 100 where Ns

Ns p

power factor of the induction motor cos W

3 VL

I L

MODEL GRAPHS:

1. Speed or slip Vs output power

2. Torque Vs output power

3. % efficiency Vs output power

S. V I Power, Speed Torque Spring% Slip Output

No. (Volts)(Amps) W

(RPM) (N-m)balance Cos Ø Power

(Watts) %ɳ(Kg) (W)

W1 W2 S1 S2

13.6 PRECAUTIONS:

1. Connections must be made tight

2. Before making or breaking the circuit, supply must be switched off

13.7 PRE LAB QUESTIONS:1. Why starter is used? What are different types of starters?

2. Compare a slip ring induction motor with cage induction motor?

3. Why the starting torque is zero for a Single Phase induction motor and non-zero of 3phase induction motor?

4. What are the disadvantages of this method?

5. Can we use rotor resistance method for starting?

POST LAB QUESTIONS:1. What is the basic principle of operation of a 3- phase induction motor?

2. What do you mean by Pullout or Break down torque?

3. What is the function of Stator?

4. What do you mean by the term Synchronous speed?

5. What is ‘slip’ in Induction motor? Why the slip is never zero in an Induction motor?

6. What is the frequency of induced current in the rotor of an induction motor at stand still and while it is running?

7. Mention the different types of Rotors?

8. What are the differences in construction between Squirrel- cage and Phase wound- rotor of an Induced Motor? What are their applications?

9. Why the rotor bars of a squirrel cage rotor are skewed?

10. What is the advantage of phase wound rotor?

11. How torque is produced in an induction motor?

12. How the starting torque of phase wound rotor does is improved?

13. What is the condition for maximum starting torque?

13.8 RESULT: Performance of curves for three phase induction motor are drawn by conducting brake test.

14. TORQUE SPEED CHARACTERISTICS OF A THREE PHASE INDUCTION MOTOR

14.1 AIM:

To determine the efficiency of 3- induction motor by performing load test. To obtain the performance curves for the same.


Sl.Equipment Type Range Quantity

No.

1 Voltmeter MI (0-600)V 1 no

2 Ammeter MI (0-10)A 1 no

10A/600V UPF 1 no3 Wattmeter Electro dynamo meter type

10A/600V LPF 1 no

4 Tachometer Digital 0-9999 RPM 1 no

5 Connecting Wires ***** ***** Required


14.4 PROCEDURE:

3. Connections are made as per the circuit diagram.

4. Ensure that the 3- variac is kept at minimum output voltage position and belt is freely suspended.

8. Switch ON the supply. Increase the variac output voltage gradually until rated voltage is

observed in voltmeter. Note that the induction motor takes large current initially, so, keep an

eye on the ammeter such that the starting current current should not exceed 7 Amp.

9. By the time speed gains rated value, note down the readings of voltmeter, ammeter, and wattmeter at no-load.

10. Now the increase the mechanical load by tightening the belt around the brake drum gradually in steps.

11. Note down the various meters readings at different values of load till the ammeter shows the rated current.

12. Reduce the load on the motor finally, and switch OFF the supply.

14.5 MODEL CALCULATIONS:

Input power drawn by the motor W = (W1 + W2) watts

Shaft Torque, Tsh = 9.81 (S1 ~ S2) R N-m RRadius of drum in mts.

2N T

sh

Output power in watts = watts60

% efficiency output power in watts x 100Input power in watts

Ns N 120 x f% slip x 100 where Ns

Ns p

power factor of the induction motor cos W

3 VL

I L

OBSERVATIONS:

S. V I Power, Speed Torque Spring% Slip Output

No. (Volts)(Amps) W

(RPM) (N-m)balance Cos ØPower %ɳ

(Watts)(Kg) (W)

W1 W2 S1 S2

14.6 PRECAUTIONS:

3. Connections must be made tight

4. Before making or breaking the circuit, supply must be switched off

14.7 PRE LAB QUESTIONS:1. Why starter is used? What are different types of starters?

2. Compare a slip ring induction motor with cage induction motor?

3. Why the starting torque is zero for a Single Phase induction motor and non-zero of 3phase induction motor?

4. What are the disadvantages of this method?

5. Can we use rotor resistance method for starting?

POST LAB QUESTIONS:

15. What is the basic principle of operation of a 3- phase induction motor?

16. What do you mean by Pullout or Break down torque?

17. What is the function of Stator?

18. What do you mean by the term Synchronous speed?

19. What is ‘slip’ in Induction motor? Why the slip is never zero in an Induction motor?

20. What is the frequency of induced current in the rotor of an induction motor at stand still and while it is running?

21. Mention the different types of Rotors?

22. What are the differences in construction between Squirrel- cage and Phase wound- rotor of an Induced Motor? What are their applications?

23. Why the rotor bars of a squirrel cage rotor are skewed?

24. What is the advantage of phase wound rotor?

25. How torque is produced in an induction motor?

26. How does the starting torque of phase wound rotor is improved?

27. What is the condition for maximum starting torque? and maximum torque under running condition?

14.8 RESULT: Torque Speed curve for three phase induction motor is drawn by conducting brake test.

15 NO-LOAD CHARACTERISTICS OF 3-PhASE ALTERNATOR

15.1AIM: To determine the No-Load Characteristics of the given three phase alternator.


Sl.No Apparatus Type Quantity

01. DC motor coupled to alternator set ----- 01 No.

02. Ammeters (0-2 amps DC) Digital 01 No.

03. Ammeters (0-20 amps DC) Digital 01 No.

04. Ammeters (0-5 amps AC) Digital 01 No.

05. Voltmeters (0-500 Volts, AC) Digital 01 No.

06. Rheostat 370 ohms/1.7 amps Tubular type 01 No.

07. Separate Excitation source(0-220V/2A DC) ----- 01 No.

08. Connecting wires ----- required

15.3 circuit diagram

15.4 PROCEDURE:In order to determine the positive sequence impedance, open circuit and short circuit tests are to be performed.

Open Circuit:

1. Connect the circuit as shown in the circuit diagram.2. Field rheostat of the motor should be kept in minimum position and single phase variac should be in

minimum output position.3. Switch on the DC supply and start the motor-alternator set with the help of a three point starter.4. Adjust the field rheostat of the motor to set motor-alternator set to the rated speed.

5. Slowly vary the Variac to increase the field excitation of the synchronous machine. Note down the value if If and V up to the rated voltage 415V.

6. Bring back the single phase Variac to the initial position, field rheostat to the minimum resistance position and switch off the MCB.

Short Circuit Test:

1. Connect the circuit as shown in the circuit diagram.2. Field rheostat of the motor should be kept in minimum position and single phase variac should be in

minimum output position.3. Switch on the DC supply and start the motor-alternator set with the help of a three point starter.4. Adjust the field rheostat of the motor to set motor-alternator set to the rated speed.

5. Slowly vary the variac such that the rated current flows through the alternator. Note down the field current and armature current.

6. Bring back the single phase variac to the initial position, field rheostat to the minimum resistance position and switch off the MCB.

15.5 Model Graph:

15.6 Tabular Columns:

A. Positive Sequence Impedance OC test

If

V

SC test

Isc

If

Plot OCC and SC characteristics and calculate the positive sequence impedance

15.7 PRE LAB QUESTIONS: 1. What is the principle of alternator? 2. What is meant by regulation? 3. What is meant by synchronous impedance? 4. What is meant by mmf? 5. How the alternators be rated?

POST LAB QUESTIONS: 1. How you determine the synchronous impedance in this method? 2. How the input to an alternator be given in your experiment? 3. Why DC supply only given to Field winding of an alternator?

4. How the frequency of an alternator is changes? 5. What is the effect of excitation on Current and Power factor?

15.8 RESULT:OCC and SC characteristics are plotted for three phase alternator.

1. verification of ohms law · web viewverification of kvl and kcl transient response of series rl...

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