A Novel Method to Detect Broken Rotor Bars in Squirrel Cage Induction Motors When Interbar Currents Are Present

This paper details the theoretical and experimental investigation into the axial force produced by broken rotor bars on copper cage rotors. It introduces interbar current theory and the overall fault progression of broken rotor bars. The paper also presents a mathematical model showing that interbar currents interact with stator flux to produce a force in the axial direction. To substantiate the model, the paper provides experimental results on several motors having broken rotor bars. The experimental results verify the frequencies postulated in the mathematical model. The measurements also show that these components are load dependent and due to interbar currents in the rotor. The experimental results suggest a new method to detect for broken rotor bars based on the presence of interbar currents. This method may be used to aid the existing methods, currently in use today.