An induction motor is also known as an "asynchronous motor", in which the rotor is placed in a rotating magnetic field, and under the action of the rotating magnetic field, a rotational torque is obtained, thereby causing the rotor to rotate.

The relative movement of an induction motor through the rotating magnetic field generated by the stator (its rotational speed is synchronous rotational speed n1) and the rotor winding. The rotor winding cuts the magnetic induction line to generate an induced electromotive force, thereby generating an induced current in the rotor winding. The induced current in the rotor winding interacts with the magnetic field to generate electromagnetic torque, causing the rotor to rotate. As the rotor speed gradually approaches the synchronous speed, the induced current gradually decreases, and the resulting electromagnetic torque also decreases accordingly. When the asynchronous motor operates in the motor state, the rotor speed is less than the synchronous speed. In order to describe the difference between rotor speed n and synchronous speed n1, a slip rate is introduced.