The slip-ring motor starters are based on the series of resistors that are applied to the rotor circuit to control the speed / torque characteristics of the motor.
Rotor starters are mainly used for the motor starting applications requiring high-starting torque like loaded belt conveyors in the mining industry. By external resistors, it is possible to shift the motor maximum (break-down) torque up to the starting torque point for motors under heavy loads during start-up. The resistors are splitted into some steps and controlled via contactors by motor starting control system. As the motor speed increases, the external rotor resistors are eliminated by shorting contactors until all external resistors are shorted out.
The slip-ring motor starters are made in two types: dry type or oil-immersed type.
3 Phase Slip Ring Rotor Starter Control & Power Diagrams
Abbreviations:
O / L = Over Load Relay
NO = Normally Open
NC = Normally Close
Three Phase Slip Ring Rotor Starter Control & Power
