| 摘要 |
PURPOSE: To obtain a protection device which can protect an over-current without making a fuse capacity large by a method wherein a reactor, for overcurrent suppression, to which a diode has been connected in parallel or a fuse is connected in series with a filter capacitor. CONSTITUTION: Normally, a difference current between a supply current on the side of a converter and a load current for an inverter flows to a filter capacitor (CF). Out of the difference current which flows to the CF, a charging current flows to a diode (DFU), and a discharge current flows to a reactor (LCF) for overcurrent suppression. In addition, in an ordinary operation, the charging current flows from the side of the converter, and the charging current flows to the side of the inverter. Normally, the load current flows via the LCF by removing a ripple portion by means of the current smoothing action of the LCF and the DFU. Then, when a phase short circuit is generated, an overcurrent in a discharge direction flows through the LCF from the CF. Then, the value of the LFU is set in such a way that a current flowing to a GTO thyristor in the phase short circuit becomes a surge-current withstand or lower. Thereby, it is possible to prevent the damage to the GTO thyristor due to the overcurrent in the phase short circuit. |
