This question needs to be discussed on a case by case basis and cannot be simply answered with “yes” or “no”.AC motors are mainly divided into synchronous motors and asynchronous motors (induction motors), and their speed characteristics are completely different when the load changes.If it is a synchronous motor: the speed is absolutely constant

Characteristic: The rotor speed of the synchronous motor is strictly synchronized with the speed of the stator rotating magnetic field (synchronous speed), without any slip.

The synchronous speed is determined by the power frequency and the number of motor poles: n=60f/p.

When the load changes: As long as the load torque does not exceed the maximum synchronous torque of the motor, the motor speed remains completely unchanged.

When the load increases, the rotor angle of the motor will slightly “lag”, but the speed will not decrease.

Conclusion: The speed remains constant.

If it is an asynchronous motor (the most commonly used AC motor): the speed will slightly decrease

Characteristic: The rotor speed of asynchronous motors is always slightly lower (in electric state) or higher (in power generation state) than the synchronous speed, resulting in a “slip rate”.

The slip rate increases with the increase of load.

When the load changes:

When unloaded: the speed is very close to the synchronous speed (such as about 1499 revolutions per minute, and the synchronous speed is 1500 revolutions per minute).

When fully loaded: the speed will significantly decrease (such as to 1420 revolutions per minute).

The magnitude of the decrease depends on the design of the motor, usually with a full load slip rate between 1% and 5%.

Note: This decrease is continuous and stable (not fast or slow), and will eventually reach a new stable speed under a new load.

Conclusion: The speed does not remain strictly constant, but slightly decreases with increasing load (exhibiting a “droop” characteristic).

3. Special exception: AC motors with variable frequency controlIf the AC motor is driven by a frequency converter and the frequency converter operates in closed-loop vector control or direct torque control mode (especially when equipped with a speed sensor):Feature: The controller inside the frequency converter will detect the motor speed in real time and automatically adjust the output frequency to compensate for the speed drop caused by the load.Conclusion: In this case, regardless of whether the motor is synchronous or asynchronous, it can achieve almost constant speed throughout the entire load range (steady-state accuracy can reach ± 0.01% or even higher).