Novel Sensorless Starting and Low Speed Drive of Cylindrical Brushless DC Motor Using Eddy Current with Un-known Load

Sensorless starting and low speed drive of a cylindrical brushless dc motor with un-known load have been a difficult problem because an electro-motive force does not arise enough at the starting and at low speeds and an inductance is constant irrespective of rotor position. In this paper, it is proposed to paste non-magnetic material and to measure a voltage of an opened phase to realize sensorless starting and low speed drives. The method is shown very feasible by experiments.