GB1269434A - Improvements in d.c. electric motors - Google Patents

Abstract

1,269,434. Electric motors. PIONEER ELECTRONIC CORP. 24 March, 1970 [25 March, 1969], No. 14252/70. Heading H2A. A commutatorless D.C. motor includes a permanent magnet rotor and at least two stator windings successively energized by a switching circuit controlled by a voltage produced in dependence on both the rotor field and the value of a current which varies with rotor speed. In the motor shown the two stator windings L 1 , L 2 , are alternately energized by transistors Tr 3 , Tr 4 , controlled by a Hall generator 3 influenced by the field of the rotor and supplied with the collector current of transistor Tr 2 . Tr 2 is controlled by a further transistor Tr 1 whose base-emitter voltage depends on the speed of rotor 4. A speed dependent voltage is fed to the emitter of Tr 1 by that one of the windings which is not driving the rotor at any given time. Speed variation may be activated by replacing R 2 with a variable resistor R 3 , Fig. 2 (not shown). Compensation for ambient temperature variation may be achieved by replacing R 1 and R 2 with resistors having a positive and negative temperature coefficient of resistance respectively, or a positive temperature coefficient resistor (R 7 ), Fig. 5 (not shown), may be inserted in the emitter lead of Tr 1 . Compensation for source voltage variation may be achieved by connecting the base of Tr 1 to a point on a voltage divider, connected across the source 2, either directly, Fig. 3 (not shown), or through an amplifying transistor (Tr 5 ), Fig. 4 (not shown).