Induction-type AC Servo Motor

The structure of an induction-type ac servo motor is identical with that of a general induction motor. If multi-phase alternating current flows through the coil of a stator, a current is induced in the coil of rotor and the induction current generates torque. In this type of AC servo motor, the stator consists of a frame, a stator core, an armature coil, and lead wire. The rotor consists of a shaft and the rotor core that is built with a conductor.

An induction-type AC servo motor has a simple structure and does not need the detector of relative position between the rotor and stator. However, because the field current should flow continuously during stopping, a loss of heating occurs and dynamic braking is impossible, unlike the AC servo motor.

Leashine ACM Series Products

The ACM series low-medium voltage AC servo motors offer high performance with models ranging from 100W to 400W. Standard  models come  with  a  standard  2500-line  or  1000-line  differential  encoder with index slits  (A, B, Z), and Hall Sensors (U, V, W). When driven by Leadshine ACS series servo drives, the ACM series motors meet application requirements from as low as 1 rpm to as high as 4500 rpm.

• Brushless construction
• Reliable industrial quality
• High torque density
• Resolution of the integrated encoders optional
• Metric 60 mm frame sizes
• Rated power from 100 W to 400 W
• Standard cabling options for direct connection to the ACS series drives

The strengths, weaknesses and characteristics of the servo motors mentioned above are summarized in Figure 1.


The rotor also has laminations; radial slots around the laminations contain the bars. As mentioned, the rotor turns when the moving magnetic field induces current in the shorted conductors, and the rate at which it rotates is the motor’s synchronous speed — determined by power-supply frequency and the number of stator poles.

Synchronous speed is the fastest theoretical speed a motor can possibly spin — when the rotor spins at the same speed as the motor’s internal rotating magnetic field. In practice, an AC induction motor is an asynchronous motor (in which the rotor lags field speed) so its rotor must spin more slowly than the field, or slip. This allows the induction of rotor current to flow, and production of torque to drive attached load while overcoming internal losses.

Induction type ac servo motors are available in fractional and integral horsepower sizes.