Noise Radiated by Electric Motors: Simulation Process and Optimization of the PWM Strategy

The noise radiated by electrical machines is due to the electromagnetic excitations applied to the structure of the machine. Even if the generated sound power levels are not as high as those typically emitted by internal combustion engines, they are characterized by the emergence of high frequency pure tones that can be annoying and badly perceived by users. The radiated noise is influenced by many parameters related to the structure and electromagnetic design of the machine. The supply strategy can play a key role as well. This paper present a 3-step simulation process. Electromagnetic excitations are estimated (finite element software) and projected onto the structure model of the machine. Dynamic response under realistic electromagnetic can be calculated. The last step is about the calculation of the radiated noise with the aid of typical acoustic methods. This simulation process is a powerful tool to predict and understand phenomena that can be complex due to the space and frequency content of the electromagnetic excitation. It can also be used to optimize the machine design. The paper focuses on the optimization of the supply strategy (PWM parameters) for a given machine. In the studied case, the noise radiated by a traction machine can be reduced by 9 dB without modifying the machine itself.