The EWM Tetrix 421 AC/DC is a digital TIG power source for alternating and direct current, liquid cooled. The description gives an adjustment range from 5 A to 420 A and continuous work from 370 A to 400 A at 40°C. The open circuit voltage is 82 V and the housing is rated IP23.
What this machine is for
This is a power source for aluminium, stainless steel and thicker parts, also for automated stations. With direct current you join mild steel and stainless steel, with alternating current aluminium and its alloys. The supply is 400 V, the cooling is by liquid, and the control is run by a digital signal processing circuit that watches the arc parameters and drives the IGBT transistors.
The description gives continuous work, that is a 100% duty cycle at 40°C, in the range from 370 A to 400 A, and a maximum current of 420 A. The mains voltage tolerance reaches from minus 25% to plus 20%, so the machine takes a weak installation and a long extension lead. The IP23 housing and the tunnel cooling of the heat sinks separate the electronics from conductive dust, which matters in a hall where machining is done.
The activArc function stabilises the arc energy. When the welder shortens the arc, the source raises the current, so the plasma pressure and the penetration grow, and the arc becomes stiff and less prone to an accidental touch of the electrode against the pool. In practice this limits the risk of tungsten inclusions and holds the heat input steady despite small hand movements, which counts on pipelines and on joints that go for testing.
The pulse reaches 15 kHz, that is 15 000 Hz. At such a frequency the plasma column narrows strongly, so thin sheet is welded faster and holds direction better. The AC Special function handles joints of very different thickness, for example 1 mm sheet with a 10 mm casting, steering the surplus energy into the thicker side and keeping the oxide cleaning on both sides. There is also a choice of wave shapes: square, sine and trapezoid, with which you set the noise level and the character of the penetration.
Features and equipment
- Digital control based on signal processing, supervision of the arc parameters and drive of the IGBT transistors.
- activArc, active stabilisation of the arc energy when its length changes.
- Pulse up to 15 kHz, that is 15 000 Hz, a narrower arc and faster welding of thin sheet.
- AC Special, an algorithm for joining parts of very different thickness.
- Choice of the alternating current wave shape: square, sine and trapezoid.
- Spotmatic, tacking without using the button on the torch, the arc strikes after the electrode touches the material, for a programmed time, which shortens tacking by 50%.
- Synergic control with a job database, after you point out the material and the thickness the machine sets the starting current, the alternating current balance and the gas parameters.
- Prepared to work with tigSpeed cold wire feeders.
- IP23 housing with tunnel cooling of the heat sinks, protection of the electronics against dust.
Technical data
| Brand | EWM |
|---|---|
| Model | Tetrix 421 AC/DC |
| Current type | AC/DC |
| Current adjustment range | from 5 A to 420 A |
| Maximum welding current | 420 A |
| Continuous work, 100% duty cycle at 40°C | from 370 A to 400 A |
| Pulse frequency | up to 15 kHz, that is 15 000 Hz |
| Open circuit voltage | 82 V |
| Supply voltage | 400 V, tolerance from minus 25% to plus 20% |
| Housing protection class | IP23 |
| Cooling | liquid |
What you get
- EWM Tetrix 421 AC/DC power source
- TIG torch 8 m in the pro version rated 350 A for alternating and direct current, liquid cooled
- Earth cable
- Mains cable
What to watch out for
The supply is 400 V and the cooling is by liquid, so before you start you check the coolant level and the flow in the torch. The torch from the set is rated 350 A and the source gives up to 420 A, so at higher settings you fit a stronger torch, otherwise the handle sets the limit of the work.
The range of functions depends on the version and the equipment of the given unit, so before you buy we check with you on the panel of this unit which modes are active. The tigSpeed cold wire feeder is not part of the set. The description does not give the weight, so arrange transport before collection. For the work you add an argon cylinder, a regulator with a flow meter and tungsten electrodes.
How we sell used machines
This unit was checked in our service workshop in Krotoszyn with measurements to PN-EN 60974-4 and a load test. The price includes the first year of the basic service package: an inspection with cleaning of the machine and a validation measurement. Further years can be added. We ship across the European Union, collection in person by appointment.
