| 摘要 |
PURPOSE:To minimize breakage of a plurality of switching elements interconnected in parallel for switching a DC power supply by providing quick action fuses in series to the respective switching elements to shut off the power supply by fusing of the fuse. CONSTITUTION:Voltage of a DC power supply 1 is switched by a plurality of switching elements TRl-TRn interconnected in parallel to be applied to an electric discharge machining gap 4. Quick action fuses Fl-Fn are connected in series to the respective switching elements. When the switching element has some failures and excessive current flows, the corresponding quick action fuse is fused. Which fuse is fused is indicated by an indicator 8, while the power supply is shut off by a breaker 9 to minimize the effect of the failure and facilitate repair. |
