How to control the speed of AC motor
How is the motor controlled?:Motor control refers to the motor start, acceleration, operation, deceleration and stop control. Depending on the type of motor and the use of the motor, there are different requirements and purposes. The motor is controlled by motor to achieve the goal of quick start, quick response, high efficiency, high torque output and high overload capacity.
The method of increasing rotor circuit startup is applicable to wound rotor, deep groove rotor and double cage rotor. For squirrel cage rotors, this method cannot be used.When increasing the rotor resistance of an induction motor, the maximum torque of the motor will not be affected, but the maximum torque will occur, and the motor torque slip curve will be compressed along the slip axis. As the motor curve shows that the slip ratio rises first and then decreases, the starting torque of the motor will increase. But its numerical value is affected by the maximum torque of the motor.The starting modes of single-phase asynchronous motor include capacitor start, resistance start, PTC start and so on.
The starting mode of three-phase asynchronous motor includes:Full voltage direct start, step-down start, increase rotor circuit resistance start.For Buck start, it mainly includes the start of autotransformer, the change of star delta and the start of variable voltage. When the asynchronous motor starts, the rotor is in a stationary state with a slip rate of s=1. At this point, the rotor resistance of the T type equivalent circuit is very low, so the starting current is larger, and the starting current can be lowered by the start of the buck. As the starting torque of asynchronous motor is proportional to the square of voltage, so it is necessary to guarantee the motor's starting ability for step-down start.
