Quality assurance testing for magnetization quality assessment of BLDC motors used in compressors

Quality assurance (QA) testing of mass-produced electrical appliances is critical for the reputation of manufacturer since defective units will have a negative impact on safety, reliability, efficiency, and performance of the end product. It has been observed at a brushless dc (BLDC) compressor motor manufacturing facility that improper magnetization of the rotor permanent magnet is one of the leading causes of motor defects. A new technique for postmanufacturing assessment of the magnetization quality of concentrated winding BLDC compressor motors for QA is proposed in this paper. The new method evaluates the data acquired during the test runs performed after motor assembly to observe anomalies in the zero-crossing pattern of the back-EMF voltages for screening motor units with defective magnetization. An experimental study on healthy and defective 250-W BLDC compressor motor units shows that the proposed technique provides sensitive detection of magnetization defects that existing tests were not capable of finding. The proposed algorithm does not require additional hardware for implementation since it can be added to the existing test-run inverter of the QA system as a software algorithm.