Single-phase motor-torque pulsations

This article gives results of a study of the vibrations of small single-phase induction motors, with a view to determining their causes and eliminating the noise which they produce. The possible sources of such vibrations were analyzed, and an experimental study was made in which the principal cause was definitely determined to be the double-frequency variation of the electro-magnetic torque developed by the motor. This variation of torque is fairly obvious when it is considered that the power input to the motor is pulsating and the output is uniform, but it was found that the torque variation at no-load was also very pronounced, a fact which does not seem to have been previously described. A description of the experiments made, a theoretical analysis of the torque variations, and a comparison of test with calculated results are given.