An AC servo motor is a two-phase AC motor, consisting of two windings: an excitation winding and a control winding. One winding is the field winding, and the other is the control winding. When in operation, a constant excitation voltage Uf is applied to the field winding, and a control voltage Uk is applied to the control winding. Once the stator windings are energized, the servo motor quickly begins to rotate. The current flowing through the field and control windings generates a rotating magnetic field within the motor. The direction of this rotating magnetic field determines the motor's direction of rotation. When the voltage applied to either winding is reversed, the direction of the rotating magnetic field changes, and the motor's direction also changes.
The stator structure of an AC servo motor is basically similar to that of a capacitor-split-phase single-phase asynchronous motor. Its stator has two windings positioned 90° apart: an excitation winding Rf, which is always connected to the AC voltage Uf; and a control winding L, connected to the control signal voltage Uc. Therefore, an AC servo motor is also called a two-phase servo motor.
Advantages:
⑴ No brushes or commutator, therefore reliable operation and low maintenance requirements.
⑵ Stator winding heat dissipation is relatively convenient.
⑶ Low inertia, easily improving system responsiveness.
⑷ Suitable for high-speed, high-torque operation.