Difference between AC Servo Motor and DC Servo Motor

Following are main difference between AC servo motor & DC servo motor

A.C. Servo Motor

D.C. Servo Motor
Low power output of about 0.5 W to 100 W. Deliver high power output.
Efficiency is less about 5 to 20%. High efficiency.
Due to absence of commentator maintenance is less. Frequent maintenance required due to commentator.
Stability problems are less More problems of stability.
No radio frequency noise. Brushes produce radio frequency noise.
Compare to DC servo motor it is relatively stable and smooth operation. It is Noisy operation.
AC amplifier used have no drift. DC Amplifier used have a drift.
AC Servo Motor Picture

AC Servo Motor Picture

DC Servo Motor Picture

DC Servo Motor Picture