What are the three methods of AC motor speed regulation?

4. Speed ​​Control Method of Wound-Rotor Motor with Rotor Series Resistance

The rotor of the linear asynchronous motor is connected in series with an additional resistor to increase the slip rate of the motor and run the motor at a lower speed. The larger the resistor connected in series, the lower the speed of the motor. This method has simple equipment and convenient control, but the slip power is consumed in the form of heat on the resistor. It is a step-by-step speed regulation with softer mechanical characteristics.

5. Stator voltage and speed regulation method

When the stator voltage of the motor is changed, different speeds can be obtained. Since the torque of the motor is proportional to the square of the voltage, the torque drops a lot, and its speed regulation range is small, making it difficult to use general cage motors. In order to expand the speed regulation range, the voltage and speed regulation should use a cage motor with a large rotor resistance value, such as a torque motor specially designed for voltage and speed regulation, or connect a frequency-sensitive resistor in series with a wound-rotor motor.

6. Speed ​​regulation method of electromagnetic speed regulating motor

The electromagnetic speed regulating motor consists of a cage motor, an electromagnetic slip clutch and a DC excitation power supply. The DC excitation power supply has a small power and is usually composed of a single-phase half-wave or full-wave thyristor rectifier. By changing the conduction angle of the thyristor, the magnitude of the excitation current can be changed.

7. Hydraulic coupling speed regulation method

The hydraulic coupling is a hydraulic transmission device, generally composed of a pump wheel and a turbine. When the pump wheel rotates under the drive of the prime mover, the liquid in it is driven by the blades to rotate. When it enters the turbine along the outer ring of the pump wheel under the action of centrifugal force, it gives thrust to the turbine blades in the same direction, so that it drives the production machinery to operate. Speed ​​regulation is achieved through different hydraulic forces (lubricating oil and turbine).