SYNCHRONIZING METHOD FOR CURRENT TYPE INVERTER WITH COMMERCIAL POWER

摘要

PURPOSE:To make it available to change a commercial power and an inverter smoothly each ther regardless of power factor of a motor load by a method wherein a pulse synchronized with the commerical power is generated, and the inverter is controlled with a pulse delayed by the power factor angle. CONSTITUTION:A comparison circuit 21 inputs a synchronous saw tooth wave proportional to the frequency of a commercial power 1 from a saw tooth wave generation circuit 18 and a phase difference detection signal from a phase difference detection circuit 20, and outputs a pulse talling at a point lagging by a rising power factor angle at the point whereat the saw tooth wave rises. A change controlling circuit 9 controls an inverter 4 with an output of oscillator 8 for which frequency rises according to the characteristic of a ramp function generator 7 at the time of activation and also with an output pulse of the comparison circuit 21 whenever frequency and phase of the inverter 4 become identical with the commercial power 1.