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Two-pulse magnetization process of the NdFeB multi-pole ring magnet for BLDC motors

Abstract

The magnetization of rare earth ring magnets forming the rotor of a BLDC or a synchronous motor requires a high level of magnetization field to achieve the desired magnetization pattern. The design of the magnetizing yoke is a compromise between the field strength requirements, the yoke temperature balance and the winding forces. The two-pulse magnetization allows reaching a higher steepness of magnetization at the pole edges and thus higher overall rotor magnetization under these difficult conditions. The magnetization fixture for the double-pulse method was designed and verified by finite element method simulations. A small series (100 pcs) of produced magnets are compared with simulations using external magnetic 3D field scanning. The artifacts (asymmetry of pole magnetization) after the two-pulse magnetization are recalculated onto unbalanced magnetic pull and torque ripple. It is shown that these artifacts do not adversely affect unbalanced magnetic pull and torque ripple, unlike the asymmetries caused by the geometric inaccuracy of the magnetizer, whose impact is crucial.

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Correspondence to Miroslav Novák.

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The result was obtained through the financial support of the European Union within the framework of the project “Modular platform for autonomous chassis of specialized electric vehicles for freight and equipment transportation,” Reg. No. CZ.02.1.01/0.0/0.0/16_025/0007293 and project Slovak Research and Development Agency APVV-18-0436.

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Novák, M., Ferková, Ž. Two-pulse magnetization process of the NdFeB multi-pole ring magnet for BLDC motors. Electr Eng 102, 2315–2323 (2020). https://doi.org/10.1007/s00202-020-01003-9

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Keywords

  • Magnetizer
  • Magnetizing process
  • Permanent magnet motors
  • Unbalanced magnetic pull
  • Magnetic field measurement