PHASE SEQUENCE CORRECTING SYSTEM FOR THREE-PHASE AC POWER

摘要

ABSTRACTThe phase sequence of a three-phase AC powersupply is detected and information representing that sequenceis stored in a memory device, such as a flip-flop. Sincethe power supply, once it is energized, may require a fewseconds to stabilize (such as may be the case when the powersource is a diesel generator), the information fed to thememory device is likely to change during the stabilizingperiod. At the end of that period, however, the storedinformation represents the true phase sequence of the ACpower supply, and at that time the information is read outand used to actuate switching apparatus to interconnect thethree-phase AC power supply to the three terminals of aphase-sensitive load (such as a three-phase AC motor) in themanner necessary to provide the load with a desired phaserotation sequence. After the stabilizing period, the inputcircuitry of the memory device is inhibited so that thestored information representing the true phase sequence willbe locked into the memory device and so that the device willbe insensitive to any fluctuating voltages, frequency ornoise that could otherwise cause an accidental phase reversalwhile the load is energized.