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ELECTRODE WELDING AND GOUGING It will be seen that the voltage drop in 100 meters 70 mm2 cable is 6 V at 250 A DC. When using longer lengths of cable, the voltage drop will increase proportionately, i.e. on a 200 meter length of 70 mm2 cable, the voltage drop will be 12 V at the same amper­ age. It should be noted that for AC current, the voltage drop can be more than double the value for DC current due to inductive resistance, especially when the welding cables lie across a steel deck. When the voltage drop is excessive, welding characteristics suffer accordingly. How large a voltage drop that can be tolerated will depend on the type of welding machine and type of electrode.

The following table shows the theoretical cable lengths relevant to

Current

Cable cross-

Section

UWI-500 TP

the different cable cross-sections and the different types of welding machines based on the following calculation: Maximum allowed voltage drop for a welding machine is: – the maximum output voltage at the corresponding current. – minus the conventional load voltage (IEC 60974-1).

The maximum length of welding cable (total length from return cable and electrode holder cable) for this voltage drop is calculated as followed: Length < voltage drop/current · conductivity of copper (58) · cable cross section.

Welding machine type UWI-320 TP

UWI-203 TP

150 A

2

35 mm 50 mm2 70 mm2

460 m 657 m 920 m

298 m 425 m 595 m

200 A

50 mm2 70 mm2 95 mm2

391 m 548 m 740 m

255 m   97 m 357 m 136 m

300 A

50 mm2 70 mm2 95 mm2

174 m   77 m 243 m 108 m 330 m

400 A

70 mm2 95 mm2

UWI-150

176 m   64 m 251 m   91 m 352 m 128 m

x) x)

4.01

x) Bring machine to work site and use short electrode/ground cables only

Note:

By connecting two cables in parallel, the voltage drop can be halved and the distance from machine to welding area thereby doubled.

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