Brushless DC motor with Hall element control - in which the control elements are switched out at set speed

摘要

The motor stator windings are fed in succession by a transistor circuit such that the permanent magnet rotor is accelerated. Hall elements on two of the winding axes provide control pulses. - The Hall elements when the set speed is reached thereby reducing the total load current drawn by the motor. The back emf in the windings, which is speed proportional, is switched via transistors to a comparator transistor. At the voltage corresponding to set speed the latter becomes conducting, and, by altering the base potential of the control transistor turns it off. This in turn alters the base current of the switching transistor by changing the potential of the voltage divider mid-point. It turns off and the Hall element control current is interrupted.