What is AC servo motor
The stator structure of an AC servo motor is basically similar to that of a capacitor-divided single-phase asynchronous motor. The stator is equipped with two windings with 90 degrees difference in position, one is the excitation winding Rf, always connected to the AC voltage Uf; the other is the control winding l connected to the control signal voltage Uc. So the AC servo motor is also called two servo motors.
The rotor of AC servo motor is usually made of squirrel cage type, but in order to make the servo motor has a wide range of speed regulation, linear mechanical characteristics, no "spin" phenomenon and fast response performance, compared with ordinary motors, it should have a large rotor resistance and small rotational inertia two characteristics. There are two types of rotor structures in use: one is the use of high resistivity conductive materials made of high resistivity conductive bar squirrel cage rotor, in order to reduce the rotor rotational inertia, the rotor into a slender shape; the other is made of aluminum alloy hollow cup rotor, the cup wall is only 0.2-0.3 mm, hollow cup rotor rotational inertia is small, fast response, stable operation, so it is widely used.
When there is no control voltage in AC servo motor, only the pulsating magnetic field generated by the excitation winding is in the stator and the rotor is stationary. When the control voltage is present, a rotating magnetic field is generated in the stator and the rotor rotates in the direction of the rotating field. The motor speed varies with the control voltage when the load is constant, and the servo motor reverses when the control voltage is in opposite phase.
Although the operating principle of an AC servo motor is similar to that of a capacitor-run single-phase asynchronous motor, the rotor resistance of the former is much greater than that of the latter. Therefore, compared with the capacitor-run asynchronous motor, the servo motor has the characteristics of three
1. Large starting torque: Due to the large rotor resistance, the torque characteristic (mechanical characteristic) is closer to linearity and has a larger starting torque. Therefore, when the stator has control voltage, the rotor rotates immediately, which has the characteristics of fast starting and high sensitivity.
2. Wide working range: stable operation and low noise.
3. No self-rotation phenomenon: As soon as the servo motor loses the control voltage, the motor will stop running immediately.