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MMM 2022

November 07, 2022

Minneapolis, United States

Torque Analysis of a Permanent Magnet Synchronous Motor using Flux Densities in Air Gap

Permanent magnet synchronous motors (PMSMs) having high power density and high efficiency are rigorously researched in various premium applications. Among PMSMs, many studies have been conducted on interior permanent magnet synchronous motors (IPMSMs) to improve torque ripple 1-3, but its accurate estimation is not straightforward. Therefore, a six-pole nine-slot IPMSM is adopted as a base model due to its popularity in academia and industries. Other two pole/slot combinations (8p/12s, 10p/15s) having the same winding factor of 0.866 are additionally selected to investigate mainly the influence of a pole/slot combination on torque performance.
Air gap force is separated into its radial and tangential components, and the tangential force density (Ft) is determined by two magnetic flux densities in air gap 4. Due to proportional relation between Ft and the torque 4, torque performance is easily identified by analyzing. In case of maximum and minimum torque at the instant of tmax and tmin, respectively, the distribution of Ft along air gap is illustrated in Fig. 1 to analyze torque ripple. The biggest gap between Ft(θm, ωtmax)and Ft(θm, ωtmin) as indicated in red and blue, respectively, occurs around the right side of a stator pole surface as shaded in yellow in case of anticlockwise rotation. Since Ft is proportional to the product of Br and Bt 4, magnetic flux densities in air gap have to be examined to analyze the variation of Ft. The moment of maximum torque is given in Fig. 2, and it is noted that the change of Bt in increasing a pole number is much greater than that of Br. Compared to Bt of 6p/9s, in particular, that of 10p/15s is significantly reduced by 46% around the right side of a stator pole, and hence, torque ripple is improved in the 10p/15s combination. In conclusion, in varying pole and slot numbers, the impact of Bt is dominant on torque ripple. Especially, the change of Br and Bt with respect to a pole/slot combination will be meticulously analyzed and explained in terms of its reason and relationship with torque ripple.

Next from MMM 2022

Vibration Analysis of a Permanent Magnet Synchronous Motor by a Pole/Slot Combination

Vibration Analysis of a Permanent Magnet Synchronous Motor by a Pole/Slot Combination

MMM 2022

Gyeonghwan Yun and 5 other authors

07 November 2022

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