Development of Rotor Core with High Magnetic Flux by Partial Non-Magnetic Improvement of Silicon Steel

Abstract

Flux leakage in the rotor core bridges is a problem specific to interior permanent magnet motors and has been unsolved till date. It is widely known that if the bridges are partially non-magnetically improved with low magnetic polarization, the leakage flux will be smaller, and the rotor will have a higher magnetic flux. We proposed that the portion of the silicon steel sheets that becomes the bridge after pressing can be nonmagnetized and laminated to fabricate the rotor core. Partially non-magnetic material with a polarization of almost zero was obtained by melting and mixing NiCr alloy powder with the silicon steel sheets. This non-magnetic improvement treatment was applied to the bridge in the rotor core sheet, in which the non-magnetic area width was 1.45 mm, and the prototype rotor core was fabricated by laminating 60 rotor core sheets. Upon measurement, the rotor core showed approximately 35% higher magnetic flux than a conventional one, with the actual value nearly identical to that obtained from the magnetic field analysis.

Suppression of Solidification Defects in Partial Non-Magnetization Improvement for Silicon Steel

“…In our previous study, 10) we proposed a new partial nonmagnetization process for silicon steel. The portion of the silicon steel sheets that become the bridge after pressing can be non-magnetized by melting and mixing the Ni-Cr alloy powder with the silicon steel sheets using a laser to fabricate the rotor core by laminating them, as shown in Fig.…”