Rotor Cage and Slip in Induction Motors
Rotor cage and slip are linked features of an induction motor: the cage carries induced rotor current, while slip is the speed difference that makes induction possible.
How they work
The cage consists of conductive bars embedded in the laminated rotor and connected by end rings. The stator's rotating magnetic field induces current in this closed circuit. Interaction between the rotor current and magnetic field produces torque.
Slip is the difference between synchronous field speed and mechanical rotor speed, usually expressed as a fraction or percentage of synchronous speed. Under motoring load, the rotor must run slightly slower than the field; if the speeds were identical, the cage would see no changing field and would not produce steady induction torque. Slip normally changes with torque, rotor temperature, and control state.
This is electromagnetic slip inside the motor, not tyre slip at the road. An induction motor may therefore have motor slip while the driven tyre has full traction.
For the complete mechanism and EV trade-offs, see Asynchronous (Induction) Motors.