Fuji Electric has developed two types of sensorless control methods for the permanent magnet synchronous motor, namely sensorless vector control and V/f control. In this paper, principles of both types of sensorless control methods are described, experimental results are presented, and the characteristics and performance of each sensorless control method are compared. Advantages of the proposed sensorless vector control include a large starting torque that is 150 % or more of the rated value and high precision torque control that has an error of 3 % or less. Advantages of the proposed V/f control are not only low hardware cost but also high efficiency and response speed, equivalent to that of sensorless vector control, realized by means of the proposed current-based high efficiency control and stabilization control.
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