Analysis and Solution on Squeak Noise of Small Permanent-Magnet DC Brush Motors in Variable Speed Applications

The phenomenon of squeaking noise, based on noise spectra data during the running up of a small permanent-magnet DC (PMDC) brush motor, is analyzed. From the analysis, it is found that apart from some mechanical issues, the major contributor of the squeaking noise of PMDC is the unbalanced magnetic radial force. In this study, the unbalanced magnetic radial force is simulated using finite-element analysis (FEA). A simple but effective method to reduce the noise is proposed. The improved method is validated by test results.