Wide speed operation of a sensorless brushless DC motor having an interior permanent magnet rotor

A PM motor drive system without position sensors has been developed, a so-called sensorless motor. Rare earth permanent magnets are not mounted on the surface of the rotor but buried in the rotor for high speed applications. The wide speed-torque range from 1000 to 5000 r/min at 4 Nm and from 500 to 10,000 r/min at no-load is realized by precisely shifting the phase angle of commutation. The system reduces vibration at starting time to 10%, compared with a conventional system. This paper describes its starting and driving characteristics to verify the validity of the theory.>