Permanent magnet motors for power density and energy savings in industrial applications

The present and future market for motors places high value on power density, operating efficiency, reliability, variable speed operation and low cost. Permanent magnet (PM) motors are now able to meet these market expectations. Compared to the prolific induction motor, PM motors provide the attributes of efficiency and reliability, plus have the additional advantages of higher power density (power per mass or volume), superior power factor (low current), low rotor temperature, and synchronous operation. Advancement in magnet technologies allows operation at higher temperatures without permanent magnetization loss. PM motors are now economically viable due to the availability of rare-earth magnets such as neodymium iron boron at lower prices. Performance comparisons between induction, surface permanent magnet, and salient pole permanent magnet motors are presented in this paper.