GB1162869A - Electrical Energy Control Circuit - Google Patents

Abstract

1,162,869. Control of D.C. motors; supply systems. MICAFIL Ltd. 3 Nov., 1967 [11 Nov., 1966], No. 50021/67. Headings H2H and H2J. The armature of a shunt-wound motor M is supplied from a rectifier bridge B1 which is connected in series with a triac Tr and an inductance L to a single-phase source. Phaseshifted pulses for controlling the triac are derived from a network comprising rectifier B2 connected to a voltage divider R12, R13, so that filter capacitor C2 is associated with resistor B1 and diode D1 to produce a smoothed direct voltage. Transistors T1, T2 provide a squarewave output which is supplied through resistor R10 to capacitors C3, C4 in the emitter circuit of a unijunction transistor T3. When switch I-O is opened, capacitor C3 is charged and discharged by the square-wave voltage at each half-wave, whilst capacitor C4 is charged to a progressively higher voltage during successive half-cycles up to the voltage to which potentiometer P is set. The emitter of transistor T3 is supplied through diode D6 from the square-wave voltage source which is reduced by the drop across the resistor R10, this drop decreasing with time so advancing the firing angle of the triac. When the transistor T3 becomes conductive, capacitor C1 discharges through pulse transformer U to the control electrode of the triac. The load may be other than a shunt-wound motor, such as a series motor, lighting circuit, or heating device.