Dynamic Measurements of an Industrial Electric Motor Stator Core

Measurements of the dynamic and acoustic behavior of a commercial electric motor stator are presented. An Allis-Chalmers motor stator core, before and after winding and potting, was excited with drives on the teeth in tangential (circumferential and axial) and radial directions. The vibration response was decomposed into its circumferential harmonics and modes of vibration. The core was mounted in a sturdy, asymmetric housing, and showed significant harmonic character. The high circumferential order ring modes of the bare stator are limited to frequencies below those of the fundamental modes of the stator teeth. When the teeth are wound and potted, however, the ring modes resemble those of contiguous cylindrical shells, increasing in frequency with mode order. Also, the vibration response of the stator decreases significantly when it is wound and potted, particularly for drives tangential to the teeth. In spite of the reductions, drives tangential to the teeth still cause vibration comparable to, and sometimes higher than, that induced by radial tooth drives.