bab 2 inductors capacitors and alternating current circuits

8/13/2019 Bab 2 Inductors Capacitors and Alternating Current Circuits

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INDUCTORS, CAPACITORS

AND ALTERNATINGCURRENT CIRCUITS

MOHAMAD TARMIZI BIN ARBAIN

MECHANICAL DEPARTMENT OF POLITEKNIK PD


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INDUCTORS


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Basic principle of inductor

Inductors: electronic component that havingproperties to apposes the current changing

Inductance: electric circuit that having properties

to appose the current changing Induction: properties that opposes the current

changing

Unit: Henry (H)

1 Henry means total inductance in coil if thecurrent changing at rate 1 ampere second andproduce 1 volt of induces voltage


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2 types of induction

Self induction

When current flow through a coil, the current will change and fluxcutting also change. This changing will produce e.m.f in a coil. Thedirection of e.m.f is apposes the source voltage direction.

SYMBOL :-


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2 types of induction

Mutual induction

When alternate current flow through coil and flux was produces. Theflux will connected to the coil B which is situated next to the coil A.Hence, e.m.f will produce in coil B.

SYMBOL :-


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Self induction formula,L

Direction of e.m.f is reverse with direction of current

E.m.f generate cause of flux changing

E.m.f generate cause of current changing

Using Faradays Law

dt

dNe

1

dt

diLe

2

21 ee

dt

diL

dt

dN

di

dt

dt

dNL


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Thus, self induction ,L

L=Nd/di L= self inductionN= numbers of turns

d/dt= flux changing

dt/di= current changing


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Energy in inductor

To find the energy in the inductor use:

Unit : Joule (J)

2

2

1LIE


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Inductors in series circuit

LT= L1+L2+L3+L4

1/LT=1/L1+1/L2+1/L3

Inductors in parallel circuit


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Effect of inductor in curcuit

To smoothing effect on the wave form of the DC curcuit

To improve transmission characteristic of wave in phoneline

Inductive strain In alternate current circuit, current will change

continuously and induces reverse e.m.f continuously.

The e.m.f will oppose the current continuously. Theopposition to the current flow by inductance known asinductive strain.

fLXL 2


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CAPACITORS

A capacitor is an electrical device which have a functionto store electrical energy

A capacitor stores energy in the form of electric field thatis established by the opposite charges on the two plates

positives charges and negative charges

Current flow direction

V C


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Capacitor basic construction

A capacitor constructed of two parallel conductive platesseparated by an insulating material called the dielectric.

SYMBOL

C

UNIT

Farad (F)

Insulator

Conductor


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Capacitance

Capacitance is a property of capacitor to

charge /electrical energy

Or the amount of charge that a capacitor

can store per unit voltage across its plates

VQC

Q= charge (coulomb)

V= voltage (volt)


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Electrical energy in capacitors

To measure the energy in the capacitor

can use equation:

QVE2

1

Q= charge (coulomb)

V= voltage (volt)

2

2

1CVE

)(2

1 2

C

QE


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Types of capacitors

Variable dielectric air capacitors

Paper capacitors

Polyester capacitorsMica capacitors

Ceramic capacitors

Electrolytic capacitors Tantalum capacitors


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Function of capacitors

Increase electrical circuit power factor

Reduces firework when is on circuit

Reduces the interference of radio repeat inpendaflour circuit.

To firm electrical current

To store electrical charge


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Capacitive strain, XC

The opposition offered by a capacitor tothe flow of current through it:-

fCXC

21

C= capacitance (F)

F= frequency (Hz)

2= constant


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Capacitors in series circuit

CT= C1+C2+C3

1/CT=1/C1+1/C2+1/C3

Capacitors in parallel circuit


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ALTERNATING CURRENT

Alternating current was current flow in two condition in positive ornegative value.

It start from zero to maximum positive, back zero and then flow tomaximum negative and flow back to zero.

AC waveform similar to the sinus waveform like below diagram

Diagram AC waveform


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From diagram AC waveform, we can

generate the equation

V(t) = Moment Voltage (volt) Vm= Maximum Voltage/peak (volt)

t = Phase Angle change to time (rad/deg)

T = 2/(second)

tVtv m sin)(


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Term In AC Voltage

Vp(peak voltage) = maximum voltage in the diagram.

Vpp(peak to peak voltage) = measured from maximumpositive to maximum negative.

Va(average voltage) = the average value for sinuswaveform. Measured taken from the area under the ACsinus line. The value was 63.7% from maximum voltage.

Vrms(root means square voltage) = the important valuein electrical circuit. Most of meter show the reading inrms value (70.7%) from the peak voltage in AC.


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Diagram AC waveform with AC term position

I cycle = 3600 = 2rad


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In phase waveform Wave A and wave B was in phase waveform because start and end

at same time. But both of it have difference maximum voltage.

tVtv p sin)( 1

tVtvp

sin)(2

A :

B :


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Out Of Phase Waveform In this case, e.m.f value in all waveform were same (Vp) but reach at maximum value

or zero value at different time.

Then it have different phase Each of waveform has difference in phase angle (and ).

Wave through zero point (0o) taken as references.

1. Wave B was references for all wave.

2. Wave A leads wave B with .

3. Wave C lags wave B with .

tVtv p sin)(

)sin()( tVtv p

)sin()( tVtv p


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Purely resistance (R)

For basic circuit use AC as poser supply, the current that flow in that circuitcan be determine by using Ohm Law

In AC resistance circuit, current and voltage in phase because no anglemovement.

Effect of resistance in the AC circuit If the resistance higher, current flow will decrease

If the resistance lower, the current flow will increase. Pure resistance will not effected the frequency of the circuit

Pure resistance circuit Pure resistance waveform Pure resistance vector


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Purely induction (L) When electric flow in the induction winding, this will become electromagnet

which will produce resistance voltage to oppose current flow.

This resistance to the current electric flow in the winding known as inductivestrain, XL.

In AC circuit if consist of induction, current will lags the volt with differentphase in 90o

The effect induction in the AC circuit

The oppose to the current work known as inductive strain and in valuesame as resistance.

Inductive strain was dependant to the frequency. Increase frequency willincrease voltage and also increase resistance.

Pure induction circuit Pure induction waveform Pure induction vector


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Purely capacitance (C)

in AC circuit consist of capacitor, current will leads of voltage in 90o. Effect of capacitor in AC circuit

Opposes to current known as capacitive strain.

Value same to the resistor resistance.

It dependent to frequency value. Which increasing frequency source,thus the capacitive strain will increase.

Pure capacitance circuit Pure capacitance waveform Pure capacitance vector


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Impedance triangle RL

Impedance define as the sum of resistance appear in ACcircuit.(symbol=Z, unit=)

It can be represent in triangle diagram to connected eachcomponent known as impedance triangle.

By using Theorem Pythagoras can be created from impedancetriangle

Impedance triangle RL diagram

fLXXRZ LL 2,22


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Current and voltage in RL series circuit.

Circuit current =

Drop voltage each component

and

Phase angle

Power factor,

ZVI

)(tan 1

R

XL

Z

Rcos

IRVR LL IXV


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RC circuit Resistance and capacitor in series connection

In the series circuit, current value same to every load. Thencurrent (I) become the reference factor.

From the figure, current will be limited by resistance ,R andcapacitive strain,XC.

This make current flow in the resistance in phase with voltage

But when current through inductive strain XLit will leads in 90o

RC series circuit RC vector diagram

22

CR VVV

IRVR

CC IXV

Resistance

voltage

Capacitive strain

voltage


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Capacitance triangle RC

From vector diagram, it can created triangleimpedance.

By using Theorem Pythagoras, capacitanceimpedance equation was

Capacitance triangle RC diagram

22CXRZ


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RLC circuit

Inductor (L), Capacitor (C) and Resistor (R) connected in seriesorder and connected to AC power supply (V).

Current (I) subjected as reference factor in vector diagram

RLC series circuit

Before draw RLC vector diagram, two (2) condition need to be define

a) Inductive strain grater then capacitive strain. (XL>XC)

b) Capacitive strain grater than inductive strain. (XC> XL)


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a)Inductive strain grater then capacitive

strain. (XL>XC)

a) Impedance circuit,

b) Current circuit

c) Drop voltage each component

d) Phase angle

e) Power factor

22)( CL XXRZ

Z

V

I

,IRVR andIXV CC LL IXV

)(tan 1

R

XX CL

Z

Rcos


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The equationsame as

previous but

change at

phase angle

(-)

)(tan 1

R

XX CL

b) Capacitive strain grater than inductive

strain. (XC> XL)

a) Impedance circuit,

b) Current circuit

c) Drop voltage each component

d) Phase angle

e) Power factor

22)( CL XXRZ

Z

V

I

,IRVR andIXV CC LL IXV

Z

Rcos

The equation

Same as previous

But change at

Phase angle (-)


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Power factor

Power factor can be phrase in percentage (%) or infraction.

Known as and rephrase as lead or lag.

is angle phase angle between voltage and current Power factor also ratio between true power to apparent

power.

Also define as ratio resistance to impedance.

Lead power factor is current lead the voltage whenvoltage taken as reference factor with +tive value.

Lag power factor is current follow voltage when voltagetaken as reference factor withtive value.

Good power factor when it value is 1.

Cos

S

PCos

Z

RCos


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Power in AC circuit

There are 3 power in AC circuit:1. Apparent power, S.

2. Active power, P.

3. Reactive power.

Apparent power, S was lost power because of resistance to make current

and voltage separate or out of phase.

Apparent power, s

Symbol : S

Unit : voltage- Ampere (VA)

Apparent power = voltage x currentVIS


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Also known as active power. Define as power use or absorb by the resistance

component in AC circuit

True power, P

Symbol : P

Unit : Watt (W)

Apparent power = voltage x current x power factor

Strain power, QAlso known as reactive power. Define as power use or absorb by the capacitor

component or inductor component in AC circuit

Symbol : Q

Unit : Voltage Ampere Strain (VAR)

Apparent power = voltage x current x sin

cosVIP

sinVIQ


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bab 2 inductors capacitors and alternating current circuits

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