Unit-wave response-based computation of magnetic noise of electric machines

The demands on modern electrical machines are continuously increasing. Electrical motors are more frequently used in variable-speed drives and thus their operation at resonant speeds has become a critical aspect, together with the increased audible noise and vibration. This poses a challenge for electrical machinery manufacturers in the form of demanding vibration and noise performance characteristics. This fact has to be taken into account in the electrical machine design process. The simulation of the electromagnetic sound power emission of an electrical machine is a three-stage process. First, the magnetic force waves in the air gap are calculated. Then a structure-dynamical model of the electrical machine is created. At this stage, the structural response, usually the vibration velocity is calculated for the magnetic excitation forces given. Finally, the radiated sound power is calculated. The traditional sound power simulation process is numerically heavy and time consuming and thus cannot be considered as an everyday or practical approach to electrical machine design. As a result, a new approach is required in order to carry out electromagnetic sound power calculation in a realistic time frame and with realistic effort. In this paper, a simplified methodology for computation of magnetic sound power based on unit-wave responses is presented, studied, and discussed.