hysteresis motor
Quick Summary
A hysteresis motor is a type of synchronous motor that uses the hysteresis effect in a solid rotor made of permanent-magnet material to achieve synchronism. These motors are often found in sound recording and reproducing machines, such as tape recorders and phonographs, as well as in clocks.12
The rotor of a hysteresis motor is typically a ring of high-carbon steel or similar semi-permanent magnet material. When the motor reaches full speed, it functions as a permanent-magnet synchronous machine. If the rotor's speed drops below synchronism, the stator's magnetic field cyclically magnetizes the rotor material around its hysteresis loop. This creates a rotor field that lags slightly behind the stator field, allowing the motor to continue producing torque.2
Hysteresis motors are known for their good starting torque, very low ripple, and quiet operation. However, they have low efficiency and are generally limited to small power applications.2
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