The Outline of AC Servo Motor Basics

By shaquila | Published on Sep 14,2015



The basics of what is AC servo motor are explained as the following states. AC servo motor, specifically designed for control systems, is a special case of the two-phase motor, a high-slip, high torque motor, which has a relatively linear torque-speed curve.

The Outline of Basic Types:

Asynchronous type

Asynchronous AC servo motor means AC induction motors. It includes a three-phase and single-phase, also can be classified into squirrel-cage type and wire-wound type. It is simply structured, and 1/2 lighter and 1/3 cheaper than DC motor in the same capacity. The disadvantage is not able to economically achieve a wide range of speed control.

This asynchronous AC in squirrel-cage type is abbreviated as asynchronous AC servo motor.

Synchronous type 

Synchronous AC induction servo motor is far more complicated, but simpler than DC motors. Its stator is similar to the induction motors, are equipped with a symmetrical three-phase winding.


The main winding and the control winding consists of the two basic winding. The main winding, usually 120 Vac, is connected to an AC source. An electronic circuit is the original power of the control winding, whose maximum voltage is about 35 Vac.Only the main winding and the control winding work simultaneously, can the motor works.


Based on the basics stated above, It would be easier to understand the following knowledge. The speed of the AC servo motor running gradually decreases with the load increases. Its working limited by the load. To put it in another way, the maximum torque reaches the top when the speed is zero, which has been reflected from the first figure. The speed influences Ac servo motor’s working efficiency.

Electronic Circuit:

Electronic circuit is the basic part of motor’s working. Electronic circuit of AC servo motor guides the direction of the motor through balancing the phase with the main winding and controls the speed by setting the magnitude of the control-winding voltage.

Control System:

Following detailed description is the control system. In order to guide it to change in prescribed ways according to arbitrary input changes, a certain physical quantity would be controlled by control systems for Ac servo motor.

If the basics of control system hasnt done a clear explanation, please search Ac servo motor controls detailed description on our website to get a more concrete answer on Ac servo motor control.

mei dou:
mei dou:
mei dou:
mei dou:
mei dou: