Seven speed control methods for three-phase asynchronous motors 3

Update:24 Aug 2019

Sixth, electromagnetic speed control motor speed contro […]

Sixth, electromagnetic speed control motor speed control method: electromagnetic speed control motor is composed of cage motor, electromagnetic slip clutch and DC excitation power supply (controller). The DC excitation power supply has a small power, usually consisting of a single-phase half-wave or full-wave thyristor rectifier. Changing the conduction angle of the thyristor can change the magnitude of the excitation current. The electromagnetic slip clutch is composed of three parts: an armature, a magnetic pole and a field winding. The armature and the latter have no mechanical connection and are free to rotate. The armature and the rotor of the motor are coaxially coupled to the active part, which is driven by the motor; the pole of the magnetic pole is connected to the load shaft and is called the driven part. When both the armature and the magnetic pole are stationary, if the field winding is made to pass direct current, a pair of magnetic poles alternating with N and S polarities will be formed along the circumferential surface of the air gap, and the magnetic flux passes through the armature. When the armature rotates with the drag motor, the armature induces a vortex due to the relative movement between the armature and the magnetic pole. The eddy current interacts with the magnetic flux to generate a torque, and the rotor with the magnetic pole rotates in the same direction, but The rotation speed is lower than the rotation speed N1 of the armature. This is a slip speed regulation method. By changing the DC excitation current of the slip clutch, the output torque and the rotation speed of the clutch can be changed. The method is suitable for production machines with medium and small power, requiring flat sliding and short time and low speed operation.

1. Simple circuit, reliable operation and convenient maintenance;

2. Smooth speed regulation and stepless speed regulation;

3. There is no harmonic influence on the power grid;

4. The speed is lost and the efficiency is low.

7. Hydraulic coupler speed control method: The hydraulic coupler is a hydraulic transmission device, generally composed of a pump wheel and a turbine, which are collectively referred to as a working wheel and are placed in a sealed casing. The shell is filled with a certain amount of working liquid. When the pump wheel rotates under the driving of the prime mover, the liquid in the liquid is pushed and rotated by the blade. When the centrifugal wheel enters the turbine along the outer ring of the pump wheel, it is given on the same steering. The turbine blades are thrust to drive the production machinery. The power transfer capacity of the fluid coupler is consistent with the relative amount of liquid in the shell. During the working process, changing the filling rate can change the turbine speed of the coupler and make stepless speed regulation. The method is suitable for speed regulation of fans and pumps.