Magnetostriction Effect on Vibration and Acoustic Noise in Permanent Magnet Synchronous Motors

This study investigates the contribution of magnetostriction to vibration and acoustic noise in interior permanent magnet synchronous motors using finite element analysis and experiments on two test machines. The two motors have identical dimensions but different iron core materials. The first motor is made of 6.5% high-silicon steel 10JNEX900 with a negligible magnetostriction (0.3 ppm at 1T), and the second motor is made of amorphous iron 2605SA1 with a significantly high magnetostriction (11.0 ppm at 1T). Using finite element analysis, the electromagnetic forces, equivalent magnetostrictive forces, and resultant vibrations are compared between the two motors. The results reveal a significant counteraction between magnetostrictive vibrations and those caused by electromagnetic forces at the multiples of the sixth vibration harmonic in the amorphous iron motor. This counteraction effect was then verified experimentally. In the experiment, the amorphous iron motor exhibited similar or even lower vibrations at the multiples of the sixth harmonic but significantly higher vibrations at other harmonics. These experimental observations can only be justified by considering magnetostriction. Such experimental evidence, which has not been reported in the existing literature, highlights the importance of accounting for magnetostriction when evaluating vibration and acoustic noise in motors.