The ESS Squarearc 276C is a used TIG AC/DC welder from the German ESS factory in Bad Waldsee: an industrial inverter cabinet with built-in liquid cooling. A square-wave alternating current, a low minimum AC frequency and 220 A at 100% duty cycle make it a machine for everyday aluminium work: tanks, frames, structures and machine parts. It has a digital WS100 panel, pulse and MMA, and the set includes an 8 m TIG torch and a 4 m earth cable.
- Digitally controlled square-wave AC. The name Squarearc describes the waveform: the current switches from one polarity to the other with a steep edge and hardly lingers around zero. The arc reignites at every polarity reversal without continuous HF, so it runs quietly and steadily. HF works only at ignition, so CNC controllers and computers next to the workstation get much less interference.
- AC frequency from 30 Hz. The rating plate of the 276C gives an AC frequency from 30 to 200 Hz. The lower limit is below that of the Fronius MagicWave (40 Hz), the EWM Tetrix and the Kemppi MasterTig AC/DC (50 Hz). At the bottom of the range the arc is soft and wide, for thick aluminium, and at the top it is narrow, for fillet welds and thin sheet.
- 220 A at 100% duty cycle. In TIG, at 40°C. That is more than the portable Fronius MagicWave 2500 and 3000 (170 and 190 A) or the Migatronic Navigator 3000 (190 A), so you run long welds on aluminium without breaks for cooling.
- Adjustable positive-pole ignition. On AC the arc starts with the electrode on the positive pole. The tungsten tip then melts into a small, rounded cap, and starts on oxide-covered aluminium are repeatable, without tungsten spatter.
- Open circuit voltage of 100 V. The same as EWM and more than Fronius (about 90 V) or Kemppi (70 V). The higher voltage makes it easier for the arc to reignite at every polarity reversal.
- Automation interface with 12 functions as standard. You can connect the FP 100 foot pedal, the FS 200 remote control or mechanised equipment.
Welding processes of the ESS Squarearc 276C
TIG AC for aluminium
Aluminium oxide melts at about 2050°C, while aluminium itself melts at 660°C. Without removing the oxide you weld as if under a crust: the metal underneath is already liquid, while the oxide layer still holds. Alternating current splits the work into two halves: with the electrode positive the arc breaks up the oxide layer, with the electrode negative it puts heat into the material and cools the tungsten.
The square waveform passes through zero very quickly, so the arc reignites immediately after the polarity reversal, without continuous HF. You can choose between two software-controlled AC waveforms.
AC frequency: from a wide spot to a narrow beam
Frequency works like the beam focus ring on a zoom flashlight. At 150 to 200 Hz the arc is narrow and stiff: it goes into the root of a fillet weld and into an inside corner instead of climbing the side walls, and on sheet from 1 to 3 mm it does not spread heat sideways. At 30 to 60 Hz the arc is soft and wide and spreads heat over a larger area: for wide multi-pass grooves on thicker aluminium and for surfacing.
TIG DC for steel
With direct current you weld structural and stainless steel. HF ignition strikes the arc without touching the workpiece, so there are no tungsten inclusions at the start. Where HF interferes with electronics, you switch to soft contact ignition, which works without an HF pulse.
Pulsed TIG on AC and DC
The current switches between the pulse current I1 and the base current I2, and you set the phase times in t1 and t2. In the hot phase the weld pool melts through, in the cool phase it partly solidifies. It works like adding and taking away heat evenly with a foot pedal, only in a steady rhythm set by the machine. You fill the gap more easily, control the root and weld in the PF and PE positions, and on thin stainless steel it is easier to keep the heat input low, which limits discolouration and distortion.
MMA with covered electrodes
For repairs, assembly work and thicker structural steel you weld with covered electrodes from 1.5 to 5.0 mm. The rating plates of the 276C give 250 A at 60% and 200 A at 100% duty cycle in MMA. You buy the electrode holder separately.
Functions and settings
- Second current from the torch. With a two-button torch you switch between the main current I1 and the second current I2 during welding. When the workpiece heats up or you reach an edge, you take heat out without a foot pedal.
- Current upslope and downslope. A gentle start without a cold beginning and without burn-through, and a filled crater at the end. On aluminium this matters, because the crater cracks easily.
- Gas post-flow. Shields the hot tungsten and the cooling end of the weld against oxidation.
- 2T and 4T modes. 2T for tack welds, 4T for long welds without holding the button.
- WS100 panel with JOB memory. LCD display with current or voltage readout, and you save the settings for repeat parts under the JOB button.
- Cooling that does not run idle. The fans switch on according to temperature, and the pump switches off a set time after welding ends. Less dust drawn into the machine and a quieter workstation.
- IP23 and S mark. Approved for work in environments with increased risk of electric shock, for example inside tanks and confined steel structures.
- Industrial build. Recessed knobs, tool-free torch change, a design that makes servicing easier, wheels, a tubular handle for moving it and a lifting eye.
How the ESS Squarearc 276C compares with other TIG AC/DC welders
The Squarearc 276C was made in Bad Waldsee from about 2006 to 2013. In the 2013 catalogue a new 276C cost 6,300 EUR, and the WS100 panel an extra 1,048 EUR. Compared with portable AC/DC machines from those years, such as the Fronius MagicWave 2500 and 3000 or the Migatronic Navigator 3000, it gives a higher current at 100% duty cycle (220 A against 170 to 190 A) and a lower minimum AC frequency than Fronius (30 against 40 Hz).
The Fronius MagicWave has more AC waveforms, and the Lorch V 27 holds 250 A at 100% duty cycle. ESS answers with an AC range starting at 30 Hz, an open circuit voltage of 100 V (Fronius about 90 V) and an automation interface with 12 functions as standard. It is a machine for a workshop that welds aluminium and stainless steel every day and needs a source for continuous work, not for occasional repairs.
Technical data
| Manufacturer | ESS Schweißtechnik, Bad Waldsee, Germany |
|---|---|
| Model | Squarearc 276C (also written as: SquareArc 276 C, ESS 276C), C stands for built-in liquid cooling |
| Type | inverter TIG AC/DC welder with pulse and MMA |
| Mains supply | 3 x 400 V |
| Mains fuse | 16 A time-delay |
| Current range | from 5 to 270 A |
| TIG duty cycle 40°C | 270 A at 60%, 220 A at 100% |
| MMA duty cycle (model rating plate) | 250 A at 60%, 200 A at 100% |
| AC frequency (model rating plate) | from 30 to 200 Hz |
| Open circuit voltage | 100 V |
| Ignition | HF or soft contact, positive-pole ignition on AC |
| Panel | WS100: LCD, JOB, I1 and I2, t1 and t2, A or V readout |
| MMA electrodes | from 1.5 to 5.0 mm |
| IP rating | IP23, S mark |
| Torch cooling | liquid, built-in unit with pump |
| Dimensions (L x W x H) | 950 x 435 x 980 mm |
| Weight (catalogue data) | 100 or 110 kg, depending on the catalogue |
What you get
- ESS Squarearc 276C power source with WS100 panel
- built-in liquid cooling unit
- TIG torch, 8 m long
- earth cable, 4 m long
What to watch out for
A 3 x 400 V connection with a 16 A time-delay fuse is enough to power it. The panel has an SP button. ESS sold a Speed Puls option up to 3000 Hz separately for this series, and it strongly constricts the arc on thin stainless steel. We will check on the running machine whether the option is active on this unit and show you the result before shipping.
ESS ended production in 2013, and we service this unit here in Krotoszyn under the service package. We do not include a gas cylinder, regulator, tungsten electrodes or filler rods. The housing has signs of use visible in the photos.
Questions about the ESS Squarearc 276C
What thickness of aluminium can I weld with the ESS Squarearc 276C?
As a rough guide, about 40 A per millimetre of thickness is assumed, so the range of the 276C covers aluminium up to about 6 mm. Above about 4 mm you bevel butt joints and weld them in multiple passes, and large cross-sections are worth preheating.
Can I weld stainless steel with it?
Yes, with direct current DC, with or without pulse. On thin stainless steel, pulse helps you keep the heat input low and limit discolouration.
Is a 16 A socket enough for it?
Yes. The machine runs on 3 x 400 V mains and needs a 16 A time-delay fuse.
Are parts and service still available for the ESS Squarearc?
ESS declared bankruptcy in 2013. In March 2014 Dinse took over service and repairs of ESS machines, but not production. We service this machine here in Krotoszyn.
How does the 276C differ from the 356C?
Both have the same controls and liquid cooling. The ESS Squarearc 356C gives 350 A instead of 270 A and 270 A at 100% duty cycle instead of 220 A, but it needs a 25 A fuse.
How we sell used machines
Unit checked in our service centre in Krotoszyn, with measurements to PN-EN 60974-4 and a load test. The price includes the first year of the service package: cleaning, basic inspection and electrical measurements. The measurement report is part of the paid service package. You can buy further years. We ship across the European Union, personal collection by appointment.
