Special Losses in Rotors of Electronically Commutated Brushless DC Motors Induced by Non-Uniformly Rotating Amature MMFS

This paper analyzes special eddy current losses induced in the rotor of an electronically commutated permanent magnet motor powered from a d.c. source, on account of the non-uniform rotation of the stator field. Formulas are established for the losses induced by the tangential component of the stator magnetic field. These formulas are applied to a specific motor design where the magnet retainment was accomplished by means of a metallic nonmagnetic stainless steel sleeve surrounding the rotor structure. The resulting losses are given with consequent conclusions.