TIG AC Frequency and Balance: What the Controls Do

What AC TIG means on a welder listing

TIG welders with an alternating current (AC) mode are the machines that listings point to for aluminum. AC means the current changes direction while welding. On a TIG machine, the changing current is what makes aluminum welding possible, because part of each cycle addresses the oxide layer that forms on aluminum. A title that says AC/DC TIG tells you the machine has that AC mode. A title that only says DC TIG is a machine without it.

For a buyer, the first question is whether you will weld aluminum. If you will, an AC/DC TIG machine is the category to look at, and frequency and balance are two of the controls those machines carry. If you weld steel and stainless steel only, a DC TIG machine is a simpler machine with fewer controls. See the AC versus DC TIG article for the difference between the two.

AC frequency and arc focus

AC frequency is the term for how many times per second the current switches direction while you weld. On a TIG welder panel and in the specification sheet, the frequency setting is shown in hertz (Hz). The control changes how focused the arc is. At a lower frequency the arc is wider, and at a higher frequency the arc is more focused. On aluminum, that makes frequency a way to choose the character of the arc for the job at hand.

The distinction that matters for a buyer: frequency is a feature of an AC/DC TIG machine, not a separate process. When a listing names frequency among its features, it is naming an adjustable control. The maker's manual describes how that control behaves on the specific model. Listings may also say square wave or sine wave, which describe the shape of the AC waveform; see the square wave article. If aluminum is your main project, the aluminum welder guide lists machines compared on stated details.

AC balance and cleaning action

AC balance is the control that adjusts how the AC cycle is split between its two parts. In an AC cycle, one portion cleans the oxide layer on the surface of the aluminum, and the other portion is where most of the heating of the workpiece takes place. The balance control lets the operator choose how much of the cycle goes to each. A setting with more cleaning action spends more of the cycle cleaning; a different setting spends more of the cycle heating.

Like frequency, balance appears on the specification sheet of an AC/DC TIG machine and in the bullet list of a listing, not in the title. The title says AC/DC TIG. The bullet list and the specification sheet name frequency and balance. That combination is the sign that the machine is set up for aluminum work.

Where the controls appear on a listing

A welder listing has three places where these controls show up. The title names the process, for example AC/DC TIG, which tells you the machine has an AC mode. The bullet list names the adjustable controls, and frequency and balance are often listed there. The specification sheet gives the range of the controls. A title that only says TIG or DC TIG is a machine without the AC mode.

Different listings for the same machine can describe the controls in different words. One bullet list may say frequency and balance, another may say adjustable AC settings. The maker's specification sheet settles what the machine carries. The adjustable settings article covers how to read a control list.

Frequency, balance and the other adjustable settings

An AC/DC TIG machine carries several adjustable settings, and frequency and balance are two of them. Pulse, synergic control, and memory channels are separate controls that can appear on the same listing. When you read a long bullet list, sorting the controls helps: frequency and balance shape the AC arc for aluminum, pulse is a separate control for the current over time, synergic control links settings together, and memory channels store your choices. The pulse article and the synergic control article explain those controls.

Questions to ask before you buy

Before you choose, read the listing for these points:

• Does the title say AC/DC TIG, or only TIG or DC TIG?
• Does the bullet list name frequency and balance, or adjustable AC settings?
• Does the maker's specification sheet describe how the two controls behave on this model?
• If the machine is a multi-process welder, does its TIG mode include AC, or is the TIG mode DC only?
• Does the machine come with a foot pedal, or is the pedal a separate accessory?
• For the settings themselves, does the maker's manual explain what each control does?

Which machines carry these controls

The machines that carry frequency and balance controls are AC/DC TIG welders and multi-process machines with an AC/DC TIG mode. Small DC TIG and stick machines do not carry them. Plasma cutter combos and MIG-only machines are separate categories. If your aim is aluminum with TIG, the aluminum welder guide covers the machines that state an AC/DC TIG mode.

For a shop or farm machine with more output, a 200-amp class AC/DC TIG machine is a common category; see the 200-amp guide. For a garage machine that can run on a 120V supply, some AC/DC TIG machines are stated as dual voltage or 120V; see the 120V guide and the dual voltage guide. A multi-process guide covers machines that combine AC/DC TIG with MIG and stick.

The maker's manual is the authority

The controls on a welder are set by the operator, and the maker's manual is the authority for how each control works on that model. Welding also falls under local rules wherever you work. For everything this article does not cover, follow the maker's manual and the local requirements for your work.

What to pick for your situation

Questions

What does AC frequency do on a TIG welder?

AC frequency is how many times per second the current changes direction. On an AC/DC TIG machine, the frequency control changes how focused the arc is, from a wider arc at a lower frequency to a more focused arc at a higher frequency. The maker's manual describes the control for the model you are reading. See the AC versus DC TIG article for the broader difference.

What does AC balance do on a TIG welder?

AC balance adjusts the split of the AC cycle between the part that cleans the oxide layer on aluminum and the part that heats the workpiece. More cleaning action gives more of the cycle to cleaning. The maker's manual explains the direction of the control on the specific machine.

Do I need frequency and balance controls to weld aluminum?

The machines listed for aluminum TIG are AC/DC TIG machines, and frequency and balance are the controls those machines carry. If aluminum is in your plans, look for a listing whose title and specification sheet state AC/DC TIG.

Can a DC TIG machine weld aluminum?

A DC TIG machine is not the category listed for aluminum, because aluminum needs the AC mode. DC TIG is the category for steel and stainless steel.

Where are frequency and balance settings shown?

On the machine panel, in the bullet list of a listing, and in the maker's specification sheet. The title usually says AC/DC TIG rather than naming the two controls directly. Read the maker's sheet to see what the control does on that model.