Why Induction motors are widely used in Industries?
Answer: In Industries 80% of the motor drives used are induction motors. Induction Motors are widely used in Industries because of some features it possess. They are:
- Low Cost
- Simple and Rugged Construction
- Absence of Commutator
- Good power factor
- Higher efficiency
- Good Speed Regulation
What is the relation between between Induction motor and Transformer?
Answer: Induction motors are considered as transformers with secondary winding rotating. This is because both transformers and induction motor operates in such a manner that power is transferred to secondary windings (rotor) from primary windings (stator) by mutual induction principle.
Why the efficiency of the Induction motor is less compared to transformer?
Answer: Induction motor and Transformer operates on the same principle that power is transferred to secondary by mutual induction. But in transformer, flux will be traveled from primary to secondary winding through the core of the transformer. In induction motor flux travels from stator to rotor through the air gap. Therefore power factor will be less for induction motor compared to transformer which also results in less efficiency for induction motor compared to transformer.
Why Speed Control of Induction Motor is difficult compared to DC shunt motor?
Answer: Speed Control of DC shunt motor can be possible by providing resistance in the armature and field circuits and varying the resistors speed changes can be carried out over a wide range. On the other hand speed control of induction motor is costlier and bit tedious.
Speed of Induction motors = (120x f x (1-s))/p.
Therefore for speed control either supply frequency should change or number of poles should change and other methods can be employed. Care should be taken that in the process efficiency and power factor should be maintained.
Explain the operation of induction motor in simple words?
Answer: When 3 phase ac supply is given to stator of the induction motor rotating magnetic field will be generated. This magnetic field (flux) cuts the stationary conductors of the rotor of induction motor. Therefore an emf is induced by Faraday's law of electro-magentism. As the rotor conductors are short circuited, current starts flowing in the windings of the rotor this produces a magnetic field. Due to interaction of both the magnetic fields a torque will be developed. If the torque generated is sufficient to overcome the load torque rotor starts rotating.
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