Experimental Study of Magnetostriction on Motor Vibration Considering Mechanical Characteristics

Magnetostriction is reported as one of the main vibration sources in electrical machines, especially in power transformers. Whereas, in electrical motors and generators, the influence of magnetostriction on electromagnetic (EM) vibration or noise is not very clear up to now. This paper is intended to give a comparative study in order to show the effect of magnetostriction on motor vibration. Two permanent magnet (PM) motors are manufactured with their stator cores made of different materials. One stator core is made of 6.5%-Si steel, which is characterized with extremely low magnetostriction. The other core is made of common silicon steel. Firstly, the two cores are wounded as single-phase transformers and excited by the same sinusoidal current. Their vibration spectrums are compared to validate their difference in magnetostriction. Thereafter, the two motors are assembled. Finite-element analysis (FEA) result shows that the electromagnetic force of the two motors are nearly identical. Since the mechanical properties is also an important issue, the experimental modal test is performed to identify related parameters of the prototypes. Finally, the operating vibration and noise of the prototypes are measured and compared. The result indicates that the magnetostriction is not the main source of vibration in electrical motors.