Aluminum Workshop: TIG welding and radio frequency interface

Q: When I gas tungsten arc-weld aluminum using AC, my portable radio speakers buzz. Does the high frequency that stabilizes the arc cause this? Will it hurt the radio or other electrical equipment? Can I shield adjacent equipment or minimize the effects?

A: The high frequency (HF) that stabilizes the AC arc does cause the buzz you hear. HRF is a low-current, high-frequency AC generated at radio frequencies, typically around 5 megahertz. In AC welding, we leave it on continuously to stabilize the arc. Although some newer AC inverters don’t need it, most GTAW machines exhibit arc instability in AC without the stabilizing HF.

HF travels through any cable or conductor electrically connected to the power supply. It also radiates back into the shop electrical input lines and is propagated through the air as a radio wave, which causes your speakers to buzz.

It definitely can damage nearby electrical equipment. For instance, if you want to use AC GTAW on an automobile, you must unplug the engine computer and other solid-state vehicle modules first. This is why you rarely see GTAW performed robotically—the HF could blow out the robot controller. To prevent this, the electronics must be “hardened” against the HF, which can be expensive.

To help minimize airborne radio frequency interference, set up and correctly adjust the spark gap that generates the HF. Always give the HF an easy and reliable path to ground by connecting the part being welded to a good building ground. Last, consider buying a newer AC inverter GTAW machine that doesn’t need continuous HF to stabilize the AC arc.