Polarity, Ground & the Electrical Circuit
Cable cross-section, ground clamp, and magnetic arc blow — the underestimated details
AI generated The welding current flows in a closed loop: machine, torch, , workpiece, ground cable. Every weak link in this chain — cable too thin, wrong polarity, poorly placed ground — takes its toll on the . These are the most common workshop errors.
The welding current flows in a closed loop: from the machine through the hose package to the , through the workpiece, back to the machine via the ground cable. Sounds simple — but it's exactly in this chain that the most common workshop errors hide, which get blamed on the machine even though they're caused by the wiring.
Cable cross-section
The golden rule: The cable cross-section must match the machine's maximum amperage. If the cable is too thin or the clamp is undersized, enormous resistance builds up at the connection points. The result: the cable starts to glow, in the worst case burns through, or a ground magnet loses its holding force due to the heat. A 200 A machine needs a correspondingly thick cable — not the thin one from an 80 A compact machine.
Ground close by
Attach the ground clamp or ground magnet always as close as possible to the joint. Every welding current generates a strong electromagnetic field. If you hang the ground meters away, you force the current to take a huge detour through the workpiece — and the kicks in: The starts hissing and dancing, breaks off, or spatters to the side. This becomes a real problem especially with DC and high currents.
Polarity
DC has two poles, and they make a difference:
• TIG: The ground goes to the positive pole, the torch to the negative pole (electrode negative, DC−). Most of the heat goes into the workpiece, penetration is deep.
• GMAW/MIG: Usually positive pole on the wire (DC+) for deep penetration — the exact polarity is given in the wire's welding data sheet.
• SMAW: Depending on electrode type DC+ (basic, cellulose) or also AC (rutile) — the print on the electrode tells you the allowed polarity.
Caution with modern inverters: Many have symmetrical sockets that look the same (originally intended for SMAW ). If the symbol is worn off, with TIG a look at the gas connection helps — it's always right next to the negative pole.
The payoff for these three details: a calm, stable , clean penetration, and no burnt cables. The circuit is the foundation everything else builds on.