equivalequivalent circuit of single-phase induction motorent circuit of single-phase induction motor

7/30/2019 EquivalEquivalent Circuit of Single-Phase Induction Motorent Circuit of Single-Phase Induction Motor

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Equivalent Circuit for Single-PhaseInduction Motors

By

AVINASH AILE N C

(1MS12ECD004)

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Equivalent Circuit

An arrangement of simple electrical components that is

electrically equivalent to a complex circuit and is used to

simplify circuit analysis

The characteristics of an induction motor, the speed,

current, starting torque, maximum torque, the motor

losses and efficiency can all be determined from an

analysis of the equivalent circuit

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EQUIVALENT CIRCUIT OF SINGLE-PHASE

INDUCTION MOTOR

Considersingle-phase inductionmotor consisting of two 3-phasestators and two cager rotor as

shown in fig

The rotor are mechanically coupledby a common shaft

Both the stator winding are

connected is series so that the same

current is flowing in the winding The direction of currents in 3-phase

stator windings, the field are

rotating in opposite direction

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EQUIVALENT CIRCUIT (CONTD)

So that, one stator winding produces forward rotating field, whereas theother produces backward rotating filed as shown in fig a

At standstill, the forward and backward rotating flux waves are equal and

the resulting torque is zero

when the rotor is stationary, the behavior of the single phase motor is

shown in fig b 4

Fig Single-phase induction motor equivalent to two three-phase motorsa b


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Equivalent circuit (contd) In the equivalent circuit, is the stator leakage impendence

is the standstill rotor leakage impedance referred to stator and

Xm is the magnetizing reactance.

The core loss is omitted and would be considered along with friction and

windage loss.

E is counter-emf induced in the main stator winding by the stationary,

pulsating flux ware produced by the combined action of both stator androtor mmfs

5Fig Single-phase induction motor equivalent at standstill


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Equivalent circuit (contd) From the double revolving filed theory at standstill, both the forward

and backward rotating flux waves are equal to half the amplitude of the

stationary, pulsating air-gap flux wave

If the forward rotating flux wave were only present then the equivalent

circuit of Fig a is obtained with the rotor stationary

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Fig Single-phase induction motor equivalent at standstill

when only backward rotating flux present, the equivalent circuit of

Fig b


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Equivalent circuit (contd)

According to double revolving field theory

both the forward and backward rotating flux

waves at standstill have their amplitudesequal to half the amplitude of the pulsating

filed.

When viewed from the stator, the effect of

equal forward and backward rotating flux

waves at standstill can be represented by animpedance in parallel with

as shown in fig a

The stator constants are also halved because

each stator carries turns.

Both the forward and waves and rotatingflux waves and rotors 1 and 2 are present,

and at the same time, the two stators are in

series, the equivalent can be connected in

series as shown in fig b

7Fig Single-phase induction motor equivalent at standstill


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Equivalent circuit (contd) From the equivalent circuit a small values of slips, is much larger than

For small values of slips, the forward-field impedance is higher than

the backward-field impendence

The increases of and decreases of at small value of slips at standstill

The forward flux wave proportional to decreases as the rotor speed

increases and it can be expressed as

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Equivalent circuit (contd)

It is helpful for the determination of stator current, motor output,

operating power factor etc

It cant be used for computing the starting torque of the motor

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Merit

Demerit


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Developed Power And Torque In Single-

phase Induction Motor

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Thank You

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equivalequivalent circuit of single-phase induction motorent circuit of single-phase induction motor

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