GB1028335A - Improvements in and relating to electric motors - Google Patents

Abstract

1,028,335. Transistor circuits. FABRIQUES MOVADO. Nov. 26, 1962 [Dec. 27, 1961], No. 44564/62. Heading H3T. [Also in Divisions G1, H1 and H2] The stator winding of an electric motor is energized from a D.C. source by transistors controlled from a pick-up device which supplies a signal in accordance with rotor position. Two transistors are used so that current can be supplied in both directions to the stator winding, which may be centre tapped, and each is controlled by a pick-up device connected to the base of each transistor, Fig. 4 (not shown). In a modification a transistor trigger circuit connects together the two switching transistors so that one is conductive when the other is blocked and only one pick-up device is needed, Fig. 5 (not shown). In a further modification again using one pick-up device a blocking transistor oscillator connected in shunt across the first switching transistor is used to control the second switching transistor, the oscillator being operative only when the first switching transistor is blocked; Fig. 6 (not shown). A further circuit using one pick-up device controlling two switching transistors relies on the voltage induced in an auxiliary winding wound on the motor stator to control the second transistor. Figs. 7 and 8 (not shown). Various types of non-contact making pick-up devices are disclosed including an inductive system where a receiver coil is shielded from a transmitter coil, energized at high frequency, by a conductive disc which has notches cut in its periphery. The induced signal being detected and amplified before being applied to the base of one of the switching transistors. Alternatively a photo-electric cell or photo-transistor may be used with in the latter case a germanium diode which effects biasing and temperature compensation. A normal transistor amplifier being used to supply sufficient power to operate the switching transistor, Fig. 19 (not shown).