A Method to Verify Accuracy of Predicted Magnetic Orientation of a Permanent Ring Magnet in a Brushless DC Motor

The paper reports a numerical and experimental method to verify the predicted magnetic orientation of a permanent ring magnet before the magnet is assembled into a brushless DC (BLDC) motor. A simple magnetic configuration, in which a permanent magnet is placed in the air without presence of any large permeability material in the vicinity, is proposed to eliminate changes in the magnetic field distribution caused by large permeability material. Based on two-dimensional electromagnetic field theory, an analytical expression is presented to calculate the magnetic field generated by a permanent ring magnet having a predicted magnetization pattern obtained by simulating magnetizing process. The calculated flux density due to the predicted magnetization pattern can be compared with the measured flux density created by the actual permanent magnet subject to the same boundary conditions. The presented method can be used to verify the predicted magnetization pattern of a permanent ring magnet without being affected by assembly process of a BLDC motor.