建筑施工用电设备中,属于单相的为数不少。其中,接于相电压的单相设备,除照明器外,还有手电钻、冲击电钻、捣固器、电锤、电动管绞板、电动曲线锯等;接于线电压的单相设备,有交流弧焊机等。在三相四线制供电系统中,这些单相设备对称连接,就能够节约 There are a large number of single-phase electrical equipment used in building construction. Among them, the single-phase device connected to the phase voltage includes, in addition to the illuminator, a hand drill, an impact drill, a tamper, a hammer, an electric tube strander, an electric jig saw, etc., and a single-phase device connected to the line voltage. There are AC arc welding machines. In a three-phase four-wire power supply system, these single-phase devices are symmetrically connected and can save