ANALYTICAL CALCULATION OF SHAFT CURRENTS IN THE MOTORS WITH HOMOGENEOUS YOKE

Abstract

Literature dealing with the matter of shaft currents mostly elaborates on the methods of motor diagnostics which only observe and analyse harmonics frequencies characteristic for shaft currents. The analytic calculation of the amplitudes of those currents has not been analysed so far for homogenous yoke motors and, in order for correct protection measures to be undertaken, it is necessary to determine exactly the parameters which influence those currents. Shaft currents are an important component of the currents which electrically damage the bearings and usually represent the dominant contribution. This is especially important for low-voltage induction motors which, according to IEC’s data, are the motors with the widest application range in the industry. In this work, the analytic calculation of shaft currents is explained for those motors.