| 摘要 |
PURPOSE:To reduce the waveform distorsion of an output voltage, by a method wherein one of two kinds of mode control signals for respective main switching elements is selected and employed alternately in accordance with the conducting direction of the output current of an inverter. CONSTITUTION:Output command signals U-W, outputted from a 3-phase sine wave generating circuit 11, are compared with a triangular wave signal C from a triangular wave generating circuit 14 by comparators 12U, 12V, 12W and become object switching signals. These object switching signals are inputted into logical circuits 19U, 19V, 19W directly and through delay circuits 16U-W, 17U-W, 18U-W and a control signal group with a control mode X and the other control signal group with the control mode Y are outputted. Then one of the control signal groups is selected alternately by a switching circuit 20U-W based on an information on the output phase of an inverter, an information indicating the zero cross point of U-phase current from a current detector 30 and respective mode switching signals outputted from a phase detection circuit 21.
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