Statistical Analysis of the Effect of Magnet Placement on Cogging Torque in Fractional Pitch Permanent Magnet Motors

Theoretically, the layout of fractional pitch permanent magnet motors should ensure the cancellation of most cogging torque harmonics. In reality, manufacturing errors lead to incomplete cancellation and higher than expected cogging torque. One potential manufacturing error is the variation in angle...

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Bibliographic Details
Published in:IEEE transactions on magnetics 2011-08, Vol.47 (8), p.2142-2148
Main Authors: Heins, Greg, Brown, Travis, Thiele, Mark
Format: Article
Language:English
Subjects:
Analytical models
cogging torque
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Forging
Harmonic analysis
Magnetic analysis
Magnetic resonance imaging
mass production
Materials science
Other topics in materials science
permanent magnet machines
Physics
Saturation magnetization
statistical distributions
Torque
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Summary:Theoretically, the layout of fractional pitch permanent magnet motors should ensure the cancellation of most cogging torque harmonics. In reality, manufacturing errors lead to incomplete cancellation and higher than expected cogging torque. One potential manufacturing error is the variation in angle between neighboring magnets. This paper uses the superposition technique to analytically determine the expected magnitude of each cogging torque harmonic based on a Gaussian distribution of angular magnet placement variation. A simple expression is presented for the expected value of each harmonic's magnitude based upon the harmonic number, the number of magnets, and the standard deviation of the Gaussian placement distribution. The derived expression is validated using Monte Carlo simulations and experimental implementation.
ISSN:0018-9464
1941-0069
DOI:10.1109/TMAG.2011.2125795