Why does the following phenomenon occur in the no-load experiment of asynchronous motors?

Asynchronous motor is a type of AC motor, in which there is a certain difference between the rotor speed and the rotating magnetic field of the stator, known as "asynchronous".
This difference allows the motor to rotate without the need for mechanical contact such as brushes or slip rings.
When the stator terminal voltage decreases, the rotating magnetic field of the stator weakens, and the rotor speed will decrease as a result. This is because the relative motion between the rotating magnetic field and the rotor causes the conductors on the rotor to generate induced currents, which interact with the rotating magnetic field to generate torque and drive the rotor to rotate.
When the stator terminal voltage decreases, the induced current will decrease, and the torque will also decrease accordingly, so the rotor speed will decrease.
Now let's explain the phenomenon of no-load current rebound.
The no-load current refers to the current of the motor when there is no load. When the stator terminal voltage decreases, although the rotor speed decreases, the motor current will rebound. This is because the decrease in stator terminal voltage weakens the rotating magnetic field, thereby enhancing the leakage magnetic field inside the motor. This leakage magnetic field will generate an induced current on the rotor, which interacts with the leakage magnetic field to generate torque and drive the rotor to rotate.
So although the speed has decreased, due to the presence of leakage magnetic field, the motor can still rotate and the current will rise slightly. So the decrease in stator terminal voltage leads to a weakening of the rotating magnetic field, causing a decrease in rotor speed. At the same time, the enhancement of the leakage magnetic field still causes torque to exist inside the motor, causing the no-load current to rise.
This is the reason for the phenomenon that occurs in the no-load experiment of asynchronous motors.