Seven speed control methods for three-phase asynchronous motors 2

Update:16 Aug 2019
Summary:

Fourth, the winding type motor rotor string resistance […]

Fourth, the winding type motor rotor string resistance speed control method: the wound-type asynchronous motor rotor is inserted into the additional resistor, so that the slip of the motor is increased, and the motor runs at a lower speed. The greater the resistance that is strung into, the lower the speed of the motor. The method is simple in equipment and convenient in control, but the slip power is consumed in the form of heat on the resistor. It has a class speed regulation and soft mechanical characteristics.

V. Stator Voltage Regulation Method: When changing the stator voltage of the motor, a set of different mechanical characteristic curves can be obtained to obtain different speeds. Since the torque of the motor is proportional to the square of the voltage, the maximum torque drops a lot, and the speed adjustment range is small, making the general cage motor difficult to apply. In order to expand the speed regulation range, the voltage regulation speed regulation should use a cage motor with a large rotor resistance value, such as a torque motor for voltage regulation and speed regulation, or a series frequency sensitive resistor on a wound motor. In order to expand the stable operating range, when the speed regulation is above 2:1, feedback control should be adopted to achieve the purpose of automatically adjusting the speed. The main device for voltage regulation and speed regulation is a power supply that can provide voltage change. At present, the commonly used voltage regulation methods include series saturation reactor, autotransformer and thyristor voltage regulation. The thyristor voltage regulation method is optimal. The pressure regulation speed is generally applicable to production machines below 100KW.