The influence of the winding type on the noise level of two-speed three-phase induction motors

The purpose of this paper is to study the influence of the type of winding - double layer or single layer - to the global noise level of the machine. For this purpose, two variable speed induction motors have been studied, of the type M3AA 71 B4/8 manufactured by Electroprecizia S.A. Săcele, Romania, with Dahlander windings, star connected - for the low speed and double star connected - for the high speed. The motors are modelled from magnetic and mechanical point of view with finite element softwares. The investigated motors were placed in the semi-anechoic chamber in order to determine the noise-to-frequency characteristics (spectrograms).