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The present and future market for motors places a high value on operating efficiency, reliability, variable-speed operation, low running temperature, quiet operation, and low cost. Permanent-magnet (PM) motors are now able to meet these market expectations across an increasing range of ratings. Compared to the prolific induction motor, PM motors provide the attributes of efficiency, reliability, etc. They also have the additional advantages of higher power density, superior power factor (low current), low rotor temperature, and synchronous operation. Advancement in magnet technologies allows operation at higher temperatures without permanent magnetization loss. The economic viability of PM motors is increasing with additional sources offering rare-earth magnets such as neodymium iron boron at lower prices. Performance comparisons between induction motors, surface PMs, and salient-pole PM motors are presented in this paper.
Date of Publication: Sept.-Oct. 2008