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Ac Induction Motor

By Emma | Published on Nov 02,2015


AC induction motor is a rotating electric machinery, with the three-phase AC power as supply.

Structure and Principle of AC Induction Motor

Most electrical fan motors are AC induction motors with two windings (coil).

The primary winding is usually used as running winding, auxiliary winding as a start winding.

AC power supply voltage is applied to start windings through starting capacitor, and due to the role of the capacitor, there will be a starting torque between the stator and rotor, making the rotor spin. The ac voltage in addition will help the stator coil to form a rotating magnetic field, and even if the current in the starting windings reduce, the rotation of motor won’t be influenced. In fact, after starting, due to the start capacitor is charged, the current in the start winding will be reduce.


1. Moderate structural complexity. There is a plurality of magnetic fields on the stator, with a squirrel-cage on the rotor.

2. The Ac induction motor can maintain high reliability (no brush wear) even at very high speeds.

3. Medium efficiency at low speed, more efficient at high-speed operation.

4. Driven by the multi-phase inverter controller

5. The Ac induction motor has Good performance of electromagnetic interference, but the performance of the inverter in EMI is poor.

6. The ac induction motor supports sensorless speed control.

7. The horsepower unit of the ac induction motor has lower costs, but higher than the single-phase AC induction motor

8. The starting torque of the ac induction motor is higher than the single-phase motor, easy to reverse the motor.


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