What defines a permanent magnet AC motor (PMAC) rotor?

What defines a permanent magnet AC motor (PMAC) rotor?

• A. It uses permanent magnets in the rotor instead of squirrel-cage bars
• B. It uses copper windings in the rotor
• C. It has no rotor
• D. It uses a liquid-cooled rotor

Answer: (A)

PMAC motors are defined by having permanent magnets fixed in the rotor, rather than rotor windings or a rotor conducting path. The stator creates a rotating magnetic field, and the interaction with those embedded magnets produces torque. This eliminates rotor copper losses and is what gives PMAC motors their high efficiency and compact, high-power density design. The magnets can be embedded inside the rotor (interior PM) or mounted on the surface (surface PM). In contrast, using copper windings in the rotor would describe a wound-rotor machine, and options like having no rotor or a liquid-cooled rotor don’t define the motor type.

PMAC motors are defined by having permanent magnets fixed in the rotor, rather than rotor windings or a rotor conducting path. The stator creates a rotating magnetic field, and the interaction with those embedded magnets produces torque. This eliminates rotor copper losses and is what gives PMAC motors their high efficiency and compact, high-power density design. The magnets can be embedded inside the rotor (interior PM) or mounted on the surface (surface PM). In contrast, using copper windings in the rotor would describe a wound-rotor machine, and options like having no rotor or a liquid-cooled rotor don’t define the motor type.