The switchboards are those in which all the live parts are installed behind the panels and
A. open
B. open front type
C. live front type
D. dead front type
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粗丝CO2气体保护焊最好选用具有平硬外特性的电源。()
CO2气体保护焊电源采用直流正接时,产生的飞溅要比直流反接时严重得多。()
摆动单道焊焊接速度慢,焊接热输入大,焊缝金属和热影响区容易过热,晶粒粗大,性能下降。()