|Authors||Jean Le Besnerais ; Vincent Lanfranchi; Michel Hecquet; Pascal Brochet|
|Status||Published in: IEEE Trans. on Magnetics|
|Keywords||Induction machine, Pulse-Width Modulation, magnetic noise, vibrations, Maxwell forces|
This paper derives the analytical characterization of Maxwell radial vibrations due to Pulse-Width Modulation (PWM) supply in induction machines, and especially in traction motors supplied with an asynchronous switching frequency. The number of nodes and the velocity of these particular force waves are experimentally validated by visualizing some operational deflection shapes of the stator. It is shown that according to the switching frequency, these forces can be responsible for high magnetic noise levels during starting and braking. A simple rule to avoid PWMnoise is then proposed, and applied to an industrial traction motor. Experimental results show that the choice of the switching frequency can have a 15 dB impact on the sound power level emitted by the motor during starting, and that a lower switching frequency can sometimes lead to lower magnetic noise. In agreement with analytical predictions, the new proposed switching frequency that avoids resonances between PWM exciting forces and corresponding stator modes reduces magnetic noise of 5 dB during starting.
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Characterization and reduction of magnetic noise due to PWM in induction machines