Effect of rotor bar shape on the performance of three phase induction motors with broken rotor bars

Abstract: A slight change in time phase shift between currents in adjacent rotor end ring segments directly affects the characteristics of the airgap torque in a squirrel cage induction machine (SCIM). On the other hand the rotor slot geometrical permeance has a strong impact on the rotor bar leakage inductance. This paper deals with effect of different rotor bar types (geometrical shapes) when a SCIM operates under healthy and broken rotor bars condition. The three phase squirrel cage induction machine is designed and modelled using two dimension (2D) finite Element Model (FEM). Static and dynamic analysis are performed in order to determine the target performance indexes such as transient torque, steady state torque, torque ripple, air-gap flux density, power factor and efficiency. The Finite Element Analysis (FEA) results evidence that the rotor bar shape can be optimized, such that the SCIM is yet to produce good performance when the phase shift between neighbouring bars e.m.f is changed due to rotor bar breakage