Describe the construction and working of AC servo motor.
AC servo motors are is wound with two windings at 900 with respect to each other. One winding is called as reference winding (fixed voltage) and the other as control winding (variable voltage). The rotor is squirrel cage with longer length and small diameter. The rotor has high resistance to increase starting torque and linear torque speed characteristics. AC servos are used for closed loop position control systems.