Optimal Design and Experimental Analysis of Rotor Casting Defect Detector

Abstract

The rotor of an induction motor, commonly known as a squirrel cage rotor, is manufactured via the die-casting process. The squirrel cage rotor comprises a rotor core, conductor bars, and end rings manufactured using either aluminum or copper via the die-casting process. Most induction motors used in industrial applications are equipped with squirrel cage rotors, which are advantageous owing to the ease of their mass production. However, when a rotor is manufactured via die casting, gas is introduced into the conductor bar and end ring areas, forming pores and shrinkage cavities. These defects adversely affect the quality of the manufactured rotors. They may result in problems during post-processing and assembly. When rotor casting defects are present, these problems can increase material costs and time loss. Therefore, this study proposes a model that can promptly detect casting defects when a rotor is manufactured. Additionally, the model enhances the size and waveform of the detection signal by optimizing the geometry of the detector core, ensuring consistent performance under the same operating conditions. An improved prototype model was designed and manufactured based on a previously studied detector model, and finite element analysis (FEA) and experimental results were compared to verify the validity of the analysis technique. Moreover, the core shape of the rotor casting defect detector was optimized, and the detection signal of the optimized model was analyzed and compared with that of the FEA. A fast Fourier transform (FFT) analysis of the detection signal of the optimized detector model shows an increase of more than ten-fold in the magnitude of the fundamental wave and more than 36% reduction in the total harmonic distortion (THD) compared to the initial model.