Awide speed range sensorless control technique of brushless dc motors for electric propulsors

This paper presents a sensorless drive technique for permanent-magnet brushless DC motors applied to electric propulsors of small ships or underwater vehicles. Propulsors enveloping electric motors (e.g., POD or subsea thrusters) have been increasingly applied due to their advantages of excellent maneuverability, high efficiency and low maintenance costs. To secure reliable operation under water, sensorless control is considered as an appropriate technique. However, conventional sensorless techniques often suffer problems of narrow speed range and low efficiency, particularly when the propulsors sustain heavy load at high speed operation. Hence, a sensorless technique with a wide speed range is developed in this paper using an enhanced commutation method. A brushless DC motor is first used to demonstrate the effectiveness of the developed technique. An electric thruster is further tested, where the results show that the efficiency matches that of the common Hall element commutation approach.