Abnormal Electromagnetic Noise of Motors depending on Fixing Methods of Permanent Magnets

Abnormal electromagnetic noise of traction motor in hybrid electric vehicle (HEV) occurred after the endurance test is experimentally investigated. Theoretical model explains that the abnormal components, which are ±1 orders of the number of slots, can be sourced from an unbalanced rotor. Experimental approach confirms that the abnormal noise is mainly from the rotor. Since there are no variations in the strength of the magnet flux, the vibration of the magnets is strongly believed as the main reason of the abnormal noise. Finally, the magnetic fixing method is changed from bond to mold, and the improvement of the noise is demonstrated