Measurement of magnetic fields in axial field motors

Measurements of the magnetic field in three axial field brushless DC motors are described. Three different magnetic materials are used in these motors. A closed-form analytical equation, which is based on a 2-D approximation, is used for calculating the flux density. The 2-D theory is shown to be reasonably good at predicting the magnetic flux density at the mean radius of the magnet for the range of axial field motors studied. For rough calculations of the field in the gap the theory is adequate. A technique for estimating the magnetization of the magnets is described