**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winding in a slip ring induction motor.Starting and speed control applications of slip ring motors has largely been superseded by variable-frequency-drives control of squirrel cage induction motors.These kind of motors are best suited for very high inertia loads, which requires a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
S

_{1 }= 0.5
1500

Slip rings are used in rotating electrical assemblies to make a continuous electrical connection between stationary and moving conductors. This enables the stationary power source to transmit electrical power to the rotating component. grandslipring

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