GB1283358A - Improvements in or relating to alternating current power supply apparatus - Google Patents

Abstract

1283358 Supply systems for consuming apparatus UNITED KINGDOM ATOMIC ENERGY AUTHORITY 3 Nov 1969 [5 Nov 1968] 52463/68 Heading H2H An alternating current power supply apparatus comprising a triggerable device, having high and low impedance states, in the supply circuit has a pulse generator connected to the device, means being provided to supply the pulse generator with a first signal representing a demand for power by the .apparatus and a second signal when the alternating supply passes through zero, the arrangement being such that the pulse generator is enabled by the first signal and operates to produce trigger pulses on the subsequent receipt of the second signal. A load, connected to terminals 15, 16, is supplied from an A.C. source 10, 11 by way of a pair of reverse parallel connected thyristors 12, 13, the gating signals for which are provided by a transformer T1 energized by a pulse generator 23 in the form of a pair of NOR gates 24, 25. The inputs to the pulse generator are at lines 26, 27, the input line 26 having a signal applied thereto from either terminal 31, 32, 33. The signal at 'these latter terminals represents a demand for power from the system and this signal when applied to the NOR gate 24 on line 26 puts the pulse generator 23 in a state ready for operation. The second signal input to the pulse generator which is applied at line 27 is derived from the A.C. supply 10, 11 at a point P by way of a zero crossing detector 36 which detects when the point P is at zero volts on the positive going part of each cycle of the A.C. supply, the detector output then providing a signal on line 27 which causes operation of the pulse generator to produce pulses which trigger the thyristors 12, 13. A bi-stable system comprising a pair of NOR gates 34, 42 is provided to ensure that the thyristors 12, 13 conduct for integral multiples of complete cycles of the A.C. supply 10, 11, the input signals for this bi-stable system being the power demand signal on line 37 into NOR gate 34 and the output signal from a second zero crossing detector 44 applied to line 43 into NOR gate 42. The output frequency of the pulse generator 23 may be forty times the frequency of the A.C. supply and the output pulses are fed through integrating, differentiating and amplifying circuits to the transformer T1 so as to shape the output pulses to have a mark/space ratio of less than 1/20.