outer arc meaning in English

外换外岛弧

The silicon controlled trigger and it s auxiliary circuit could regulate simultaneously the controlling coil current of four series - parallel connected powers , so the purpose of making four powers output in step with was achieved , and the process of increasing progressively current after lighting arc and weakening current after going out arc was realized
利用可控硅触发器及辅助电路可以同时调节串并联在一起的四台电源控制线圈的电流，达到四台电源同步输出的目的，并且实现了等离子弧喷涂引弧时电流递增和熄弧时电流衰减的过程。