| 摘要 |
PURPOSE:To make it possible to control an inverter even during a prolonged instantaneous power failure, by a method wherein a smoothing capacitor of an inverter main circuit is constituted by two series-connected capacitors, and the voltage between the neutral point thereof and one phase line of output lines of the inverter is employed as an inverter control power source. CONSTITUTION:The voltage generated an AC power source 1 is insulated by a transformer 6, which a connected to a power failure detecting circuit 27. To form a power source for an inverter control circuit 140, the AC power source 1 is connected to the primary side of a transformer 26 through a-contacts 321, 323 of a changeover relay 32, and connection is made such that a DC voltage of an inverter main circuit, i.e., the voltage between a neutral point 300 formed by capacitors 3A, 3B and one of inverter output terminals, e.g., the U phase is supplied to other taps on the primary side of the transformer 26 through b-contacts 322, 324 of the changeover relay 32. The voltage provided by a secondary winding of the transformer 26 is rectified as well as smoothed and supplied to the inverter control circuit 140. |
