| 摘要 |
PURPOSE:To reduce in size and cost an inverter by reducing the number of current detectors required for controlling to correct an output voltage of a three-phase voltage type inverter according to output current. CONSTITUTION:A single-phase current detector 4 is provided in an arbitrary one phase of three phase outputs of a three-phase voltage type inverter 2 to detect its output current, and positive/negative polarity of the detected current is detected by a current polarity detector 5. With respect to other two-phase output currents, both the currents are disposed in a vector manner by a phase difference of 120 degrees with the detected current, and the sum of the three vectors becomes zero. Thus, positive and negative polarity relationship of the two-phase output currents is operated to be estimated based on the positive/negative polarity relationship of the detected currents by a three-phase current polarity operator 6, and a predetermined correction amount is output by deciding an adding/subtracting direction in a predetermined phase to an output voltage target value of corresponding phase according to the positive/negative polarity relationship of the three-phase output currents by a three-phase voltage correction signal output circuit 7, thereby obtaining a new voltage target value with respect to the three-phase output voltages. |
