Five speed control methods for three-phase asynchronous motor
According to the formula of the three-phase asynchronous motor speed: n=60f/p(1-s), we can know that the speed of the three-phase asynchronous motor is related to the frequency f, the pole pair p and the slip s, and adjust any one of them. The speed will change. The speed control method of FA157 reducer three-phase asynchronous motor can be roughly divided into variable frequency speed regulation, variable pole speed regulation and change slip speed regulation.
Three-phase asynchronous motor speed control method 1: frequency control
Frequency conversion speed regulation is a speed control method that changes the frequency of the stator power supply of the motor and changes its synchronous speed. The main equipment of the variable frequency speed control system is the frequency converter that provides the variable frequency power supply. The frequency converter can be divided into two categories: AC-DC-AC inverter and AC-AC inverter.
The frequency conversion speed regulation of gear reduction motor is different according to the control mode, which can be divided into U/f control, slip frequency control, vector control and direct torque control.
Three-phase asynchronous motor speed control method two: variable pole speed regulation
The speed control method is to change the stator winding connection mode to change the stator pole number to achieve the purpose of speed regulation, change the pole pair number P of the stator winding, and the synchronous speed n1 changes, for example, the pole pair number doubles, the synchronous speed It is reduced by half, and the speed of the motor is also reduced by about half. Obviously, this speed control method can only change the speed at the first level and one level, instead of smoothing the speed.
Three-phase asynchronous motor speed control method three: change the slip rate
There are many ways to change the slip rate S, which can roughly summarize the following
1, GIS cascade speed control method
The cascade speed regulation of the reducer refers to the adjustment of the additional potential in the rotor circuit of the wound-type motor to change the slip of the motor and achieve the purpose of speed regulation. Most of the slip power is absorbed by the added additional potential, which is then used to generate additional means to return the absorbed slip power to the grid or convert energy for use. According to the slip power absorption and utilization mode, the cascade speed regulation can be divided into the motor cascade speed regulation, the mechanical cascade speed regulation and the thyristor cascade speed regulation mode, and the thyristor cascade speed regulation is often adopted.
2. Winding type motor rotor string resistance speed regulation method
The wound-type asynchronous motor rotor is inserted with an additional resistor to increase the slip of the motor and the motor operates at a lower speed. The greater the resistance that is strung into, the lower the speed of the motor.
3, stator voltage regulation method
When the stator voltage of the motor is changed, a different set of mechanical characteristic curves can be obtained to obtain different rotational speeds.
