GB1499044A - Electrical generators - Google Patents

Abstract

1499044 Supplying loads from generators ENGINE APPLICATIONS Ltd 31 Aug 1976 [27 Nov 1975] 48852/75 Heading H2H An automatic control system wherein a generator produces electrical energy when a load is connected to the generator comprises an oscillator, the output of which is inductively coupled to the output leads of the generator such that when a load is connected to the output leads the magnitude of the oscillator output signal is varied, a detector for detecting the oscillator output and means for sensing the level of the detector output and arranged to actuate switching means which cause the generator to produce electrical energy when the detector output changes by a given amount. The output of an oscillator 20 which includes a transistor 21 energized from a battery output terminals 10, 11 by way of an operational amplifier 12, is inductively coupled to one or more output leads 32, 33 of an electric generator by way a transformer 30 and to a diode detector 40. With no load connected to the generator output leads 32, 33, the output frequency of the oscillator 20, preset by a variable resistor 27, has a value such that a relay 60 is un-energized. When a load is connected to the leads 32, 33 a high frequency current will flow in the circuit comprising the load, leads 32, 33 and a capacitor 35. This will cause a decrease in the amplitude of the output oscillations of the oscillator 20 which decrease is detected by the diode detector 40 with the result that the output of an operational amplifier 44 drops for a short time, say one second, determined by the rate of charge of a capacitor 45. The drop in potential at the output of amplifier 44 causes conduction of a transistor 54 so that a capacitor 55 is rapidly charged to render transistors 58, 59 conductive thereby to energize a relay 60 which causes starting of a prime mover driving the generator which applies electrical energy to the load connected to the leads 32, 33. When the output of the amplifier 44 returns to its original value after the predetermined delay, the transsistor 54 again becomes non-conductive, conduction of transistors 58, 59 being maintained by the discharge of the capacitor 55 whereby energization of the relay 60 is maintained to allow the generator to produce an output on leads 32, 33. Such an A.C. output causes a square wave to appear at the output of the amplifier 44 whereby transistor 54 is alternately switched on and off to maintain the charge on the capacitor 55 and the relay 60 energized.