Effect of Rotor bar Shape and Stator Slot Opening on the Performance of Three Phase Squirrel Cage Induction Motors with Broken Rotor Bars

Abstract: Stator slot opening width has an impact on the airgap magnetic field, a poor choice of this design parameter can results in distorted airgap magnetic field and increased space harmonics. This will in turn affect the overall performance of three phase squirrel cage induction machine (SCIM). On the other hand changes in rotor bar geometry results in different resistances at various depths of the rotor bar and this yields increased or decreased electromagnetic torque. This paper aims to investigate the effect of different rotor bar types (geometrical shapes) and stator slot opening widths 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 transient analysis are performed in order to determine the target performance indexes such as transient torque, steady state torque, torque ripple, power factor and efficiency. The Finite Element Analysis (FEA) results evidence that both the rotor bar geometrical shape and stator slot opening can be optimized, such that the SCIM is yet to produce good performance when the phase shift between neighboring bars e.m.f is changed due to rotor bar breakage