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What is the principle of AC servo motor?

August 12,2022

The structure of the stator of AC servo motor is basically similar to that of capacitor split-phase single-phase asynchronous motor.

Its stator is equipped with two windings with different positions, one is excitation winding Rf, which is always connected to AC voltage Uf; The other is the control winding L, which is connected to the control signal voltage Uc. Therefore, AC servo motors are also called two servo motors.

The rotor of AC servo motor is usually made of squirrel-cage type. However, in order to make the servo motor have a wide speed regulation range, linear mechanical characteristics, no “self-rotation” phenomenon and fast response performance, it should have two characteristics: large rotor resistance and small moment of inertia compared with ordinary motors. At present, there are two kinds of rotor structures that are widely used: one is squirrel-cage rotor with high resistivity conductor made of high resistivity conductive materials, and in order to reduce the moment of inertia of the rotor, the rotor is made slender; The other is a hollow cup rotor made of aluminum alloy, with a thin cup wall of In order to reduce the reluctance of the magnetic circuit, a fixed inner stator should be placed in the hollow cup rotor. The hollow cup rotor has a small moment of inertia, quick response and stable operation, so it is widely used.

When AC servo motor has no control voltage, there is only pulsating magnetic field generated by exciting winding 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 speed of the motor changes with the control voltage. When the phase of the control voltage is opposite, the servo motor will reverse.

Although the working principle of AC servo motor is similar to that of split-phase single-phase asynchronous motor, the rotor resistance of the former is much larger than that of the latter.

Therefore, compared with single-machine asynchronous motor, servo motor has three remarkable characteristics:

And the starting torque is large.

Because of the high resistance of the rotor, its torque characteristic curve is shown in the figure, which is obviously different from that of ordinary asynchronous motors. It can make the critical slip s >, which not only makes the torque characteristics (mechanical characteristics) closer to linearity, but also has a larger starting torque. Therefore, when the stator has a control voltage, the rotor rotates immediately, which is characterized by fast starting and high sensitivity.

And the operation range is wide.

No rotation phenomenon.

Normal operation of servo motor, as long as the control voltage is lost, the motor stops running immediately. When the servo motor loses its control voltage, it is in a single-phase running state. Because of the high resistance of the rotor, the two torque characteristics (T-S curve) and the resultant torque characteristics (T-S curve) produced by the action of two rotating magnetic fields rotating in opposite directions in the stator and the rotor.

The output power of AC servo motor is generally.-W. When the power frequency is Hz, the voltage is V, V, V; When the power supply frequency is Hz, the voltages are V, V, V, V and so on.

AC servo motor runs smoothly and has low noise. However, the control characteristics are nonlinear, and because the rotor resistance is large, the loss is large and the efficiency is low, compared with the DC servo motor with the same capacity, it is only suitable for. -W low-power control system.The AC servo motor cannot operate without the AC servo driver, the AC servo driver plays a vital role.We also have some other products such as linear guide .If you need it, please contact our motor manufacturer.