Cogging Torque Investigation of PM Motors Resulting from Asymmetry Property of Magnetic Poles

Daikoku Akihiro, Yamaguchi Shinichi

doi:10.1541/ieejias.127.95

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Other Title

PMモータの磁極の非対称性に起因するコギングトルクの検討
PMモータの磁極の非対称性に起因するコギングトルクの検討--永久磁石の個体間ばらつきの影響評価
PM モータノジキョクノヒタイショウセイニキインスルコギングトルクノケントウエイキュウジシャクノコタイカンバラツキノエイキョウヒョウカ
—永久磁石の個体間ばらつきの影響評価—
—Influence of Performance Variation between Permanent Magnets—

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Abstract

This paper examines the cogging torque of a permanent magnet (PM) motor resulting from the asymmetry property of magnetic poles, which comes from the performance variation between magnets. A PM motor with 32 poles (= 16 pole pairs) and 36 slots is selected for verification, because the motor whose pole/slot ratio is 8/9 is sensitive to the performance variation between permanent magnets. Assuming that two different magnetization levels of magnets are mixed together in one rotor, the amplitude of the 2.25th and 4.5th components of cogging torque, which show 36 (=2.25 × 16) and 72 (=4.5 × 16) times of pulsation per rotation respectively and both of which result from the asymmetry property of the magnetic poles, are evaluated. As a result, it was clarified that the cogging torque characteristics depend upon the alignment pattern of the two kinds of magnets. The amplitudes of the 2.25th and 4.5th components of cogging torque are proportional respectively to the amplitude of the 36th and 72nd components of the squared magnetic flux density around the rotor which is set in the space. Using the proportional constants found from the finite element analyses in some alignment patterns, the cogging torque amplitudes of the motors with other alignment patterns can be predicted only by calculating the squared magnetic flux density around the rotor. The predicted cogging torque amplitudes correspond to the actually calculated results.

Journal

IEEJ Transactions on Industry Applications

IEEJ Transactions on Industry Applications 127 (1), 95-102, 2007

The Institute of Electrical Engineers of Japan

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