Slip ring induction motor - advantages and disadvantages of slip rings induction motor - Electrical input

Sunday, August 5, 2018

Slip ring induction motor - advantages and disadvantages of slip rings induction motor

                                                  Slip ring induction motor 

Slip ring induction motor:-- is a type of induction motor in which rotor winding are connected through slip rings to the outer resistance. slip rings induction motor is easier to start than squirrel cage motor. by adding resistance in series with rotor winding, the starting current can be low to maintaining the starting torque, insertion of resistance in the rotor ckt of an induction motor help to increases its torque .Resistance is reduced at the full speed, when motor speed high. Both stator and rotor have three phase winding in a slip ring induction motor.Starting and speed control applications of slip ring motors has largely been superseded by variable-frequency-drives control of squirrel cage induction motors.These kind of  motors are best suited for very high inertia loads, which requires a bow-out torque at almost zero speed.its working principle is the same as for other induction motors.






                                  Slip ring induction motor symbol






   Advantages of slip ring motor:-

1.slip ring induction motor speed can be controlled easily as compare to squirrel   cage induction motor .

2.bow-out torque can be achieved from 0 RPM(Rotation Per Minute)

3.squirrel cage induction motor takes high starting current at full load but slip   ring induction motor takes low starting current at full load.

4. slip ring induction motor has high starting torque as compare to squirrel cage  motor.



   Disadvantages slip ring induction motor:-

1. slip ring induction motor is quite expensive than squirrel cage induction    motor .

2. it requires periodic maintenance of the brushes, slip rings , external rotor    resistance etc.

3. slip ring motor needs large space for the motor and its control




Numerical slip loss :- 



If the speed of a 125 kW. 1480 r.pm. motor is varied at constant torque to 750 r.p.m.. then the additional slip loss ---

= 125 x (0.50 — 0.0133)

= 125 x 0.4867

= Or 61 kW

Where,
                 S =  __1500 – 1480__       = 0.0133  S1 = 0.5

                                    1500





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