Equivalent Circuit of Induction Machines

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Equivalent Circuit of Induction Machines

• EE 341 Energy Conversion
• Ali Keyhani
• Induction Machines
• lecture 2

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Equivalent Circuit of Induction Motor

• Assumptions
• Both stator and rotor have 3-? Y-connected
  windings.
• The stator is fed from a 3-? source.
• The subscript 1 refers to the stator and 2
  refers to the rotor.

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a) Standstill condition
Suppose the rotor is at standstill (that is rotor
is stationary, ?m0). Using transformer theory,
the equivalent circuit for 1-? to ground is
shaft
4
a) Standstill condition
Normally Xm and Rm are very large and net Zm acts
as open circuit. Therefore, they are ignored and

Standstill
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b) Rotor is free to rotate
Suppose rotor speed is ?m. And R2 R2,rotor Rext
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b) Rotor is free to rotate
Where R1 stator resistance/? X1 ?s L1 stator
reactance/? I1 stator current (line) E1
induced emf/?
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b) Rotor is free to rotate
Relationship between I1 and I2, and E1 and
E2 Define
You can show that
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b) Rotor is free to rotate
So
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Reduced circuit model
Multiply by a
Divided by s
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Reduced circuit model
But from the stator equation
So
Lets define
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Reduced circuit model
The induction machine equivalent circuit is
Stator
Rotor