How a slip ring motor work?

The stator coil is exactly the same as a 3 phase induction motor. The difference being the rotar which has 3 phase wiring in star point or delta connection and also has the sliprings connected to the wiring of the rotor. Brushes are use for the contact between the surpply and the rotor. By controling the current we can control the torgue and speed of the motor. This is done with resistance. Resistance can be greated by means of a resistance bank, liquid resistance or a variable resistance. The basic Idee is: The higher the resistance, low starting current, high torque, high % slip. Motor runs slowly

Low resistance , Higher starting current, lower torgue, lower % slip Motor runs faster.

Thus by varing the rotor resistance the motor can be adapted for a spesific load.

The motor Are mainly used for Overhead cranes, Elevators in buldings, Pumps under pressure and large fans