| 摘要 |
PURPOSE:To reduce switching loss effectively by controlling the PWM signal generating operation for each phase based on a power factor angle determined to follow up the peak value of phase current in an inverter load for a predetermined interval. CONSTITUTION:A phase difference detecting section 30 detects the phase difference between a phase voltage VU and a line current IU, i.e., a power factor phi, for phase U. The power factor phi is fed to a current command generating section 32 which generates current commands IULAMBDA, IVLAMBDA, IWLAMBDA for controlling the switching stop interval of an inverter 10 depending on the power factor phi. An adder 34 generates a line current IV, being fed to a subtractor 18V, based on the line currents IU and IW and the phase difference detecting section 30 operates a power factor phi based on the line voltage VUV and the line current IU. The switching stop interval is set at 60 deg. which is equal not to the interval between the peaks of phase U voltage VU but to the interval between the peaks + or -30 deg. of phase U line current. Phase V and phase W are also subjected to similar processing. This constitution reduces switching loss effectively. |
