GB951367A - Electric power supply installation - Google Patents

Abstract

951,367. Automatic control of current and voltage. BETEILIGUNGS-UND PATENTVERWALTUNGSGESELLSCHAFT m.b.H. Aug. 3, 1962 [Aug. 9,1961], No. 30031/62. Heading G3R. A load 1 is supplied from a D. C. generator 3 having a field winding 4 fed with pulsating direct current derived from the generator 3 by way of slip rings 6, a transformer 7, an air-gap choke 8 and a rectifier 5. A controlled rectifier 11 connected across the field winding 4 is responsive to a control voltage which is the difference between a reference voltage, derived from a Zener diode 15, and the voltage across a resistor 17 carrying the load current. When the load current is below a predetermined value at which it is to be maintained constant, the control voltage is not sufficient to make the rectifier 11 conductive, and the generator is fully energized; however, when the current reaches the predetermined value, the increased control voltage causes rectifier 11 to conduct, and the field winding 4 is effectively short-circuited whereby the generator output falls. With a decreasing load current, the control voltage decreases and the rectifier 11 then reverts to its non-conductive state when the pulsating direct voltage of the rectifier 5 passes through the zero value. This cycling action continues to maintain the load current at a constant value. The currentdependent voltage may be derived from a choke with a biasing winding (Fig. 2, not shown). The supply source may be an A. C. generator (Fig.3, not shown). In a modification, Fig. 4, both the output voltage and the load current are kept constant; the conduction of rectifier 11 is controlled by a current dependent voltage derived from a choke 27, 28 a rectifier 25 and a resistor 24, and the conduction of a further rectifier 45 is controlled by a voltage proportional to the output voltage at the circuit points 12,16 and derived from a voltage divider 40,41. The arrangement is such that either the rectifier 11 or the rectifier 45 is rendered conductive when the load current or output voltage exceeds the respective predetermined value. A single controlled rectifier with associated diodes may replace the rectifiers 11 and 45, and the circuit for derivihg the currentdependent voltage may include a transistor (Figs. 5 and 6, not shown). The supply source may be an A. C. network (Fig. 9, not shown), in which case the A. C. load current is maintained constant by controlling the biasing current of a choke in the supply line.