Regarding automobile drive train, it becomes important that hydraulic pressure works "on-demand" to reduce gas emission and save fuel. For this purpose, electric pump units should be adopted instead of engine-driven pumps. In order to use an electric pump unit in the drive train, a motor must have enough reliability on heat-resistance, dust-proof and the likes. Therefore a brushless motor without using hall sensors is desirable for automobile drive train applications. But some technical means are needed to drive sensorless-brushless motor. This paper describes the developed method to drive brushless motor without hall-sensors.
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