There are two types of AC motors with completely different conclusions
Asynchronous induction motor (universal AC motor for range hood and fan) changes load, and the speed will definitely change, which cannot be kept constant
The synchronous speed is fixed by the power frequency and pole pairs: \ (n1=\ dfrac {60f} {p} \)
Actual rotor speed (n<n1), with slip rate present;
Load increases → slip increases → actual speed slightly decreases;
The load decreases and the speed increases.
Ordinary range hood AC plastic sealed motors belong to this category, and the full load speed will be slightly lower than the no-load speed.
2. Synchronous AC motors (permanent magnet synchronous, reluctance synchronous) have a constant theoretical load change speed, which is equal to the synchronous speed
The rotor magnetic field rotates synchronously with the rotating magnetic field, without any slip. As long as the voltage and frequency are stable, the speed of light and heavy loads remains basically unchanged;
Disadvantages: Overloading can easily cause stepping loss and sudden drops in speed.
Add key distinctions (applicable to range hood motors): Single phase asynchronous AC motors are standard for range hoods on the market. As the load (air duct resistance, oil pollution blockage) increases, the speed drops significantly, and the air volume decreases accordingly;
Only high-end variable frequency range hoods use permanent magnet synchronous motors, which maintain stable speed under load fluctuations.
Summary of ordinary household range hood AC asynchronous motor: load changes, speed is not constant;
Synchronous AC motor: maintains a constant speed within the rated range.