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Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
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An induction motor can be said analogous to
transformer
synchronous motor
universal motor
stepper motor
transformer
An induction motor is considered a generalized transformer with a rotating secondary. Like a transformer, the primary (stator) induces a voltage in the secondary (rotor) via electromagnetic induction without any direct electrical connection.
An induction motor is considered a generalized transformer with a rotating secondary. Like a transformer, the primary (stator) induces a voltage in the secondary (rotor) via electromagnetic induction without any direct electrical connection.
s=NsтАЛNsтАЛтИТNrтАЛтАЛ тАФ Slip calculation in induction motors
E2тАЛ=4.44f╬жN2тАЛ тАФ Induced emf equation principle analogous to transformers
In a transformer, the primary winding produces a time-varying magnetic field that links with the stationary secondary. In an induction motor, the stator winding (primary) creates a rotating magnetic field (RMF) that induces emf in the rotor conductors (secondary). The fundamental difference is that the induction motor includes a mechanical degree of freedom (rotor motion) to convert electrical power into mechanical torque.
Both devices rely on Faraday's Law of Electromagnetic Induction.
The stator of the induction motor acts as the primary winding of a transformer.
The rotor of the induction motor acts as the secondary winding.
Energy transfer is purely inductive, requiring no physical contact between stator and rotor.
Rugged construction
Self-starting capability (in most polyphase designs)
Low maintenance due to absence of brushes
Cannot operate at exactly synchronous speed
Requires reactive power for excitation
Industrial pumps and fans
Conveyor systems
Compressors
| Feature | Transformer | Induction Motor |
|---|---|---|
Coupling | Magnetic | Magnetic |
Secondary State | Stationary | Rotating |
The induction motor is essentially a 'rotating transformer' where the secondary frequency changes with slip.
Option B is incorrect because a synchronous motor requires DC excitation for the rotor.
Option C is a series-wound commutator motor capable of operating on AC or DC.
Option D is a precise position-control motor with discrete rotational steps.
A is correct тАФ The induction motor operates on the principle of electromagnetic induction exactly like a transformer, with the stator acting as the primary and the rotor as the secondary.
Always remember that in an induction motor, if the rotor is locked (NrтАЛ=0), it behaves exactly as a short-circuited transformer.