CIRCUIT ARRANGEMENT FOR SUPPLYING POWER TO A LOAD FROM A PLURALITY OF AC POWER SOURCES

摘要

1399756 Systems comprising two or more A.C. sources TELEFONAKTIEBOLAGET L M ERICSSON 7 Sept 1972 [7 Sept 1971] 41663/72 Heading H2H A system for supplying power to a load 10 from either or both in parallel of two A.C. sources 11, 12 comprises two back-to-back pairs of controllable rectifiers 19, 20 and 21, 22, the rectifiers being rendered conductive in a manner so as to supply the load with alternating current from whichever of the two sources has the higher voltage. The rectifiers may be thyristors or thyratrons or equivalent devices and the A.C. source 12 may be an inverter. When the load 10 is resistive the thyristors 19, 22 are rendered conductive during the whole of the relevant half cycles of the sources 11, 12, but if the load 10 is inductive they are rendered conductive only during the portions of the half cycles when the voltage applied to the load has the same polarity as the current flowing through the load. When the terminals X11, X12 are positive and Y11, Y12 negative thyristors 19, 21 are made conductive by the application of, gating pulses thereto. If the potentials at terminals X11, X12 are equal both sources 11, 12 will supply the load 10 in parallel. If the potential of X11 is higher than that of X12, the load 10 will be supplied by the source 11 only. If the potential of X12 is above X11 then the source 12 supplies the load. In the next half cycle when Y11, Y12 are positive the thyristors 20, 22 are rendered conductive and the load 10 receives power of opposite polarity. Voltage peaks in the reverse direction across the thyristors are avoided by means of resistors R1 and capacitors C1 in parallel therewith. Voltage stabilizers may be incorporated into the system arranged to stabilize either the supply voltages or the load voltages. The gating signals for the thyristors may be derived from the sources 11, 12 by way of circuits including transformers and transistors or alternatively may be derived from the load voltage or the current flowing in the load. Circuits are described for producing gating pulses according to whether the load is resistive or inductive.