Advantages and Disadvantages of Induction Motor

Advantages of Induction Motor

1. The most important feature of an induction motor is that it is very simple in construction. The stator construction of the  induction motor  is similar  to the construction of  stator of the  Synchronous motor.However, a slip ring is required to feed DC Supply to feed DC voltage to Synchronous Generator rotor.  These Slip rings are not required in  a Squirrel  cage induction motor because the windings are permanently short circuited. However, the slip rings are required in the case of wound rotor induction motor. The squirrel cage induction motor does not have slip rings and brushes and, therefore it requires very less maintenance. 
2.  The induction motor is robust and its performance does not affect with environmental conditions.
3. A Squirrel cage induction motor  has few numbers of parts as compared to other types of motors. The Squirrel cage induction motor does not have slip rings, carbon brushes and commutator, therfore the cost of the Squirrel cage induction motor is low as compared to other types of motor. However, in a slip ring or Wound rotor type induction motor slip rings are used to add external resistance to the rotor winding to get higher starting torque. 
4.  The Squirrel cage induction motor does not have slip rings and carbon brushes. The sparking between the slip ring and brushes may happen in the case of slip ring or DC motor. In the case of Squirrel cage induction motor sparking is absent, therefore the motor can be operated in hazardous conditions.
5. The three phase induction motor has a high starting torque, good speed regulation. The motor is almost a constant speed motor and it gives bery good speed regulation. The motor has reasonable overload capacity.
6. The efficiency of an induction motor varies between 85 to 98 %.

Disadvantages of Induction Motor

1. A single phase induction motor can not generate the rotating magnetic field and hence it is not self starting motor. Some auxilaries are required to make the single phase induction motor self starting. 
2. The induction motor takes high reactive power at no load operation and its power factor is very low at no load or light load. At start,the motor draws large magnetising current  and the power factor is low. The power factor gets improved when the loading on the motor is increased.
3.  The induction motor is almost a constant speed motor, and the speed control of induction motor is very difficult to attain beacuse there is slight change in the speed for the entire loading range.However, the induction motor is best suited for speed control if used with variable frequency drives 
4.  The induction motor draws large magnetizing current at start. This can cause system voltage drop if power system rating is not proper.  
5. The strating torque of the Squirrel cage induction motor is low and hence it is not used for the applications which require high starting torque. However, slip ring induction motor can be used for starting the loads which demand high starting torque.

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