The cylindrical permanent-magnet rotors of DC brushless motors aremagnetized in special patterns for the main-field region and thecommutation-field region so as to provide starting torque reducecogging, and minimize losses. The resultant magnetic-field patterns aredifficult to measure accurately as a function of axial andcircumferential position. A measurement system is described which wasdeveloped to make such measurements on a series of small DC brushlessmotors. The system utilizes a Hall probe for sensing the radial ortangential-B components of the field, a synchronizing device, anoscilloscope for display and digitizing data and a computer forprocessing and printing out the data. An example is shown of a typicalreadout of the radial-B field for a motor magnetized in the N-S-O-N-S-Opattern. The system is designed for checking on the field strength ofthe magnets, the required pattern, and the correlation between themain-field and commutation-field patterns
展开▼
