What is unique about AC servo motors compared to ordinary motors?
The structure of the AC servo motor stator is basically similar to that of a capacitive split phase single-phase asynchronous motor. The stator is equipped with two windings with 90° difference between each other, one is the field winding Rf, which is always connected to the AC voltage Uf; the other It is the control winding L, which is connected to the control signal voltage Uc. Therefore, the AC servo motor is also called two servo motors.
The rotor of the AC servo motor is usually made into a squirrel-cage type, but in order to make the servo motor have a wide speed range, linear mechanical characteristics, no "rotation" phenomenon and fast response performance, it should have compared with the ordinary motor. Two characteristics of large rotor resistance and small moment of inertia. At present, there are two types of rotor structures that are widely used: one is a squirrel-cage rotor made of a high-resistivity conductive material made of a high-resistivity conductive material, and the rotor is made slender in order to reduce the moment of inertia of the rotor; One is a hollow cup rotor made of aluminum alloy, the cup wall is very thin, only 0.2-0.3mm. In order to reduce the magnetic resistance of the magnetic circuit, a fixed inner stator is placed in the hollow cup rotor. The rotor has a large moment of inertia, a fast response, and a smooth operation, so it is widely used.
When there is no control voltage in the AC servo motor, only the pulsating magnetic field generated by the field winding is present in the stator, and the rotor is stationary. When there is a control voltage, a rotating magnetic field is generated in the stator, and the rotor rotates in the direction of the rotating magnetic field. When the load is constant, the rotational speed of the motor varies with the magnitude of the control voltage. When the phase of the control voltage is opposite, the servo motor Will reverse.
