| 摘要 |
PURPOSE:To improve a power factor and to make a capacity of a device smaller by providing a chopper between a direct current reactor and a three phase bridge inverter device. CONSTITUTION:A chopper 10 is inserted between a direct current reactor 4 and a three phase bridge inverter device 5 in parallel to these, an igniting angle alpha of thyristors constituting the three phase bridge inverter device is made fixed and a chopper control circuit 11 to vary ''on'' ''off'' periods of the chopper by an instruction of a speed instruction device 6 is provided. A slip S is to be controlled by controlling ''on'' ''off'' periods of the chopper, a feed back electrical power SP2 to an electrical power source 2 from the secondary side of a wound type induction motor 1 through a converting device 9 is fed back as a power factor of cosalpha as an igniting angle of the three phase bridge inverter is alpha, an ineffective power at this time becomes to SP2 tan(pi-alpha), accordingly an ineffective power becomes smaller as an igniting angle alpha reaches as nearer as pi, a power factor can be improved and a capacity of a device can be made smaller. |
