By Mike Sammons, TIG Product Manager — Miller Electric Mfg. Co.
Q: I’ve heard that inverters let me adjust the arc to stay in the electrode negative mode for up to 90% of the AC cycle. Can this really improve my travel speed?
A: Absolutely. You can increase travel speed, get better penetration or both because inverters let you direct about 25% more heat into the weldment in the same
amount of time. When welding at 100 amps, an inverter like the Dynasty™ DX essentially gives you 125 amps of welding power.
Q: Why do inverters have an “adjustable output frequency” function?
A: Increasing the output frequency (which conventional machines cannot do) creates a tighter and more focused arc cone, directing the heat into a smaller area.
In fact, you can get better penetration and reduce the size of the weld profile. This may let you increase travel speed, use less filler metal and reduce or eliminate
pre-heating, pre-weld beveling and post-weld grinding.
Q: I don’t have much room in the shop, and my incoming power is at capacity. Would an inverter be a good solution?
A: Yes. For example, the Dynasty DX has a footprint of 17 in. x 12.5 in. x 24 in. and weighs only 90 lb. Even better, it draws just 26.3 amps of 230 V three-phase
primary power to create a 250 amp Squarewave output. A conventional Squarewave machine, which only accepts single-phase power, draws 92 amps on the primary side.
In 1974, Miller Electric invented and patented the Squarewave™ AC output and balance control function found on their Syncrowave® series of TIG welders. Squarewave technology
made the transition through the zero amperage range faster than a regular sine wave, which improved arc starts and created a more stable arc. With balance control, the operator
could change the duration of the AC half cycle, adjusting the electrode negative (EN) from 45 to 68%.
Now Miller introduces the next generation of technology with their new AC TIG inverter, which features three advanced Squarewave capabilities. First, it produces incredibly smooth,
stable arcs because the Squarewave is driven through the zero point thousands of times faster than a rectifier-based welder. Miller’s Dynasty™ DX is so fast that its built-in high-frequency
capabilities are used for arc starting only.
Second, inverter-based welders extend EN balance control. The Dynasty DX lets operators fine-tune duration times from 50 to 90%. Making the EN portion of the cycle last longer:
- Achieves greater penetration.
- Narrows the weld bead.
- May increase travel speeds up to 20%.
- May permit using a smaller diameter tungsten to more precisely direct the heat or make a narrower weld bead.
- Reduces the size of the etched zone for improved cosmetics.
Less EN time produces greater cleaning action to remove heavier oxidation, lessens penetration for work on thin materials and widens the bead profile.
Third, inverter-based welders let operators adjust the welding output frequency, from 20 to 250 Hz in the case of the Dynasty DX. Conventional welders have a fixed output of 60 Hz.
Lowering the frequency produces a broader arc cone, which widens the weld bead profile and better removes impurities from the surface of the metal. Increasing frequency above 60 Hz produces a tight,
focused arc cone. This drives more heat into the weldment for better penetration, and it narrows the weld bead, which helps when welding in corners, on root passes and fillet welds.
Note that when AC TIG welding with an inverter, the operator should treat the tungsten as if the weld were being made in the DC mode: select a 2%-type tungsten (thorium, cerium, etc.) and grind the electrode to a point.
Electricity likes to come off a point, which further improves controlling the weld puddle. For example, a skilled welder can make a 1/8 in. fillet weld on 1/8 in. aluminum plate with a pointed electrode.
For more information on the Dynasty DX, AC TIG welding, or a free copy of our White Paper, “New controls for AC TIG welders,” call 1-800-4-A-MILLER (1-800-426-4553, ext. 602).
Information courtesy of Miller Electric