A hysteresis Motor

• A. Can not be run in reverse speed
• B. Need DC excitation
• C. Is a constant speed motor
• D. Is not a self-starting motor

Answer: (C)

The hysteresis motor can be considered as a self-starting synchronous motor. From the time of starting until it reaches synchronous speed, the motor produces a synchronizing torque and an ideally flat speed/torque characteristic. Due to the absence of slots and teeth on the rotor, the operation of this motor is smooth and quiet.
 
The motor behavior is similar to that of a conventional synchronous motor but there is no excitation winding on the rotor or permanent magnets, giving the motor a high efficiency and power factor. These characteristics make it ideal for many industrial applications, such as in electronic and medical equipment, tape and video recorder drives, computer drives, clocks, gyroscope rotors for inertial navigation, robotics and other special applications where precision and reliability are required.