GB896932A - Control of supply to an inductive load - Google Patents

Abstract

896,932. Automatic control systems. LANCASHIRE DYNAMO ELECTRONIC PRODUCTS Ltd. March 3, 1960 [March 13, 1959], No. 8843/59. Class 38 (4). A control system comprises a transistor amplifier arranged to regulate the mean current supply to an inductive load by switching from a low power output condition to a high power output condition and vice versa at intervals so regulated as to control the effective current supply, a smoothing rectifier being connected in parallel with the load in conjunction with an inductance connected in series with the supply to prevent the flow of an excessive reverse current through the rectifier due to the capacitance thereof. As shown, the load comprises the armature of a motor M having an interpole winding 1, an inductance L1 and a resistance R2, the rectifier D1 being connected across the load and an inductance L2 being connected in series with the supply. The armature current is regulated by output transistors T6 controlled by transistors T1 and T2 arranged as a bi-stable multi-vibrator trigger circuit having one condition wherein the transistors T6 are switched to deliver maximum current and another condition wherein the output is switched off or reduced to a low value. A source 3 of negative voltage is provided, and a feed-back from the armature circuit is obtained by means of a potential divider 4 and is fed into an integrating circuit 5, the outputs from the source 3 and the circuit 5 being transmitted to the transistor T1 through resistances 6 and 7. The action is such that when the transistors T6 deliver maximum current the current fed back from the potential divider 4 to the junction-point 8 of the resistances 6 and 7 rises, whereas during minimum output the feed-back current falls, and the potential shift at the base of the transistor T1 acts to vary the output from the transistors T6 to oppose any deviation in the armature current. Specification 871,999 is referred to.