Causes and Characteristics of the Electromagnetic Vibration of A Squirrel Cage Induction Motor under Loaded Condition.

Abstract

The three-phase squirrel cage induction motor (IM) has been used in all types of industry, because of robustness and simplicity of its structure, lower cost and easiness of maintenance. Due to the resultant air gap flux wave, IM produces electromagnetic vibration and noise more or less regardless of slot-combination. Recently, reduction of electromagnetic vibration and noise becomes important subject from standpoint of environmental improvement.Vibration caused by IM at no-load has been studied for many years and its basic factors have been analyzed. However, electromagnetic vibration under loaded condition is not analyzed enough. Since vibration under loaded condition are affected by load and installation, analysis of this vibration is rather difficult task. But study of electromagnetic vibration of motor itself under loaded condition is basically most important item.This paper clarifies theoretically and experimentally causes and characteristics of the electromagnetic vibration of IM under loaded condition. Firstly, general equations are derived for dominant electromagnetic force waves that produce electromagnetic vibration. Cause and vibration mode are clearly classified and theoretical analysis is provided basic concept of electromagnetic vibrations.Secondly, the electromagnetic vibrations for various loads are measured, taking the effect of natural frequency of the motor into consideration. These measured data are classified and analyzed in detail, based on the proposed theory.