A position and speed sensorless control using the counter electromotive force of permanent-magnet motor (PM) debases the control performance at a low speed. We will propose a controllable system at full speed, including a zero speed using saliency.At low speed, the sensorless control is made by observing a current ripple at a time when alternating voltage has been applied to a salient-pole motor. Also, for discriminating the S and N poles of the magnet, magnetic saturation is used. A device has been applied to the motor rotor to allow the magnetic saturation to come about easily.Furthermore, at a time of high speed, drive at a full-speed range has been accomplished by switching smoothly over to a sensorless driving system making use of counter electromotive force. All algorithms are implemented by software, and this system can operate successively from starting to high-speed operation.Shown herein are the operational principles at a low speed, analysis and experimental results, the control scheme, how to changeover the control mode at a high speed, and the experimental results.Index Terms-Permanent-magnet motor, salient pole, sensorless drive.

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