Three common types:
1. Special frequency conversion motor, this is to use the inverter frequency conversion to achieve the speed regulation of the motor. The speed regulation range is large and continuous, and the precision is high.
2. The speed regulating motor itself has several terminals, and the different terminals are controlled by the speed switch to realize the adjustment of the motor at different speeds. The speed regulation is fixed and the speed regulation range is not very convenient. Is the two-speed motor high and low two files
3. There is also the use of a governor, which uses mechanical means to achieve speed control through the meshing of different diameters. This function is similar to the second one.
4. Voltage regulation, this voltage regulation is not the working voltage of the motor, but the excitation coil voltage. This speed regulation accuracy is also very high. It is commonly used in universities to do experiments.