YRKK series ac slip ring induction motor, also known as three-phase wound rotor AC asynchronous motor, must be connected in series with resistors or reactors in the motor rotor circuit in order to reduce the starting current, increase the starting torque, improve the power factor, and effectively improve the motor starting performance. Therefore, in mechanical equipment with large capacity and high requirements for rotational torque, this type of electric motor is usually used for dragging.