Permanent Magnet Motor VS. Induction Motor Efficiency

As the name implies, a permanent magnet motor uses permanent magnets on the rotor. The alternating current applied to the stator results in rotation of the rotor. Because the magnets are permanently magnetized, the rotor can run synchronously to the switching AC current. The slippage necessary in induction motors is eliminated, improving your heat efficiency.

The inherent efficiency of a permanent magnet motor is higher than an induction motor. Both motors use a three-phase design through fully optimized performance. Induction motors, however, were designed to work primarily at 60 Hz. As you up the Hz in high-frequency induction motors, eddy current losses will be far greater than in well-made permanent magnet motors.

The design of brushless permanent magnet motors provides 2-3x more power density (torque) than induction motors, with about 50% fewer core losses. Regardless of how you bend or shape an induction motor, a well-designed, synchronous permanent magnet motor will offer increased range, better performance, and so on.

Permanent Magnet Motor VS. Induction Motor

Permanent Magnet Motor Materials

In the permanent magnet, a rotor can now be a solid piece made from press-and-sinter powder metallurgy magnetic material. You can design the rotor in such a way as to have the magnets glued to the outer diameter or encased within the rotor.

It doesn’t have to be made from electrical steel laminations! A powder metal rotor can have the slots designed via the net-shape nature of powder metal, eliminating any need for costly machining. By using sintered soft magnetic material, a powder metal rotor for a permanent magnet motor can achieve strength similar to competing processes.

Rotor material for induction motors,  however, still consists of stamped electric steel laminations. The stamping process results in far more scrap waste than powder metallurgy, and core losses increase as you stack more sheets.

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