Influence of pole-pair number and rotor slot number on effects caused by cage faults

This paper discusses the relationship between the pole-pair number `p´ and the slot number `N´ as well as basic effects in stator currents caused by various cage faults. The analysis is performed using a model of a motor with faulty cage reduced to four equations. It is capable of operating with cage asymmetry factors. The authors show how additional component in stator currents depend on asymmetry factors. The relations between those factors and numbers of pole-pair and rotor slots are found based on design data of cage motors. As a result in the paper the authors present a set of curves relating the asymmetry factor for one broken bar to the slot number for a given pole-pair number. The paper also shows a method for estimating the effects due to multi-bar faults. All considerations were carried out by estimating the effects due to cage faults in the simplest possible manner.