The Migatronic Pi 250 DC HP is a used TIG DC and MMA welder from the Danish manufacturer, built for precision work on stainless and structural steel. The HP panel gives you three types of pulse, including fast pulse up to 523 Hz and Synergy PLUS controlled with a single knob, and the TIG-A-TACK function tacks austenitic steel with a short pulse instead of several seconds of heating. The set includes a liquid cooling module, a trolley, a 4 m TIG torch and a 4 m earth cable.
- TIG-A-TACK with the manufacturer's method. A tack lasts from 0.01 to 2.50 s, with HF ignition, no upslope and no pulse. Together with Damstahl, Migatronic developed a method for tacking austenitic stainless steel pipe: from 0.02 to 0.1 s at a current 2 to 3 times higher than for welding. Such a tack is about 10 amp-seconds (175 A for 0.06 s), while an example manual tack at 60 A for 3 s is 180. At a similar arc voltage that is more than ten times less heat in the workpiece, which means less discolouration and a lower risk of losing corrosion resistance at the tack.
- Three types of pulse on one panel. Conventional pulse with independent pulse and pause times, fast pulse from 25 to 523 Hz, and Synergy PLUS, where you set only the peak current.
- Bi-Level up and down. You switch to the second current, from 10 to 200% of the main current, with a short press of the torch button in 4T. In the Kemppi MasterTig MLS (from 10 to 90%) and the Fronius TransTig the second current is only used to lower the current.
- 250 A from a 10 A fuse. The source draws at most 13.0 A from the 3 x 400 V mains at a power factor of 0.94, so it runs from any CEE 16 A socket with margin to spare, much like the Kemppi MasterTig MLS 3000. On site you need a generator of at least 13.5 kVA with electronic voltage regulation.
- 20 programs with lock. 10 TIG programs and 10 MMA programs. You can lock programs P3 to P10 and the whole panel, so the welder cannot change parameters approved by the welding engineer, even on a shared workshop machine.
Welding processes of the Migatronic Pi 250 DC HP
TIG DC with HF or LIFTIG ignition
Direct current from 5 to 250 A for stainless and structural steel. HF ignition strikes the arc without the tungsten touching the workpiece, so no tungsten inclusions are left in the weld. If the electrode is touching the material, the machine will not send the HF pulse.
LIFTIG strikes the arc by touching and lifting the electrode, without an HF pulse. Migatronic intended it for places sensitive to interference, for example near controllers and measuring equipment.
Fast pulse up to 523 Hz: a narrower, stiffer arc
The current switches between the peak current and the base current (from 10 to 90%) from 25 to 523 times per second. The weld pool does not have time to cool between pulses, so it responds to the average current, while the arc responds to the peak current. Because arc force rises with the square of the current, at the same average current a pulsed arc is narrower and stiffer. It works like the water from a garden hose when you squeeze the end: the same flow, but a concentrated jet.
In practice you get a stable arc at low currents and a higher welding speed, a narrow weld and a narrow heat-affected zone on thin stainless sheet and thin-walled tubes. During fast pulse the display shows the average current.
Synergy PLUS: pulse with one knob
You set only the peak current, and the machine selects the main pulse parameters by itself, continuously. It works like a camera in aperture priority mode: you set one value, and the automatic system selects the rest. Changing the current during a job does not require setting the pulse again, so the pulse character stays the same across the whole batch of parts. Migatronic describes the arc sound in this mode as clean and metallic, without the tiring buzz of pulse.
Conventional pulse: a rhythm for adding filler rod
You set the pulse time and pause time independently from 0.01 to 10 s, which gives from 0.05 to 50 pulses per second and any phase ratio. In the base current phase the weld pool partly solidifies, so positional welding is easier, you fill the gap more easily when the fit-up is poorer and you add filler rod in time with the pulses. The weld face gets a regular ripple pattern.
TIG-A-TACK: tacking austenitic steel
A short, strong arc pulse fuses the edges at a small point without filler metal, like TIG spot welding cut down to hundredths of a second. The heat does not have time to spread through the workpiece, and the hot spot has almost no time to oxidise on the root side. The tacks are small and disappear in the finishing weld.
On pipe and sheet in grades 1.4307, 1.4404, 304L and 316L, the Migatronic method lets you tack without backing gas on the root side, provided the gap is less than 0.2 mm, there is no edge misalignment and the parameters are within a qualified WPS. Shielding gas in the torch is always required. On carbon, ferritic and duplex steel, and on V-grooves in thick walls, you tack the conventional way, with filler metal.
MMA with Hot Start, Arc-power and Anti-freeze
With a covered electrode you weld at currents from 5 to 250 A. Hot Start raises the current by up to 100% above the setting for 0.5 s at the start, so the electrode strikes cleanly. Arc-power adds current only at the moment of short circuit (up to 100%, for example 40 A plus 50% gives 60 A), so the short arc does not go out and the electrode does not stick. If the electrode does stick to the weld pool, Anti-freeze lowers the current so that you can break it free easily. Conventional pulse also works in MMA.
Weld cycle settings
- Spot Time from 0.01 to 20 s. Measures the welding time at the main current, so short, repeatable welds get the same amount of heat every time.
- Start current from 1 to 200%. A soft start on thin sheet or a hot start on a thick workpiece that draws heat away quickly.
- Upslope and downslope from 0 to 20 s, end current from 1 to 90%. A filled crater and a lower risk of crater cracks at the end of the weld.
- Gas pre-flow from 0 to 10 s, post-flow from 0 to 20 s. Post-flow protects the hot tungsten and the end of a stainless steel weld against oxidation. You can open the gas valve from the menu to purge the torch and check the regulator.
- 2T and 4T modes. The 2019 manual describes 6 variants of 4T, including 4T-REPEAT, which keeps the arc burning after the downslope, so you start the next cycle without striking the arc again. The number of variants depends on the software version.
How the Migatronic Pi 250 DC HP compares with other TIG DC welders
The Fronius TransTig 2500, EWM Tetrix 300 DC and Kemppi MasterTig MLS 3000 are from the same class. All three have a higher current at 100% duty cycle (from 200 to 210 A against 150 A), Fronius and EWM pulse faster (2 kHz and 15 kHz), and Kemppi pulses up to 300 Hz.
What sets the Pi 250 DC HP apart is TIG-A-TACK with a manufacturer-developed method for tacking stainless steel pipe, and the Bi-Level second current up and down (Kemppi MLS only down, from 10 to 90%, Fronius TransTig only lowering). It is a welder for precision work on stainless steel, pipe prefabrication, service and installation, not for hours of welding thick plate at high current.
Technical data
| Manufacturer | Migatronic, Denmark |
|---|---|
| Model | Pi 250 DC HP, TIG DC HP panel (also written as: PI 250 DC, Pi250) |
| Type | inverter TIG DC and MMA welder with pulse |
| Mains supply | 3 x 400 V, ±15%, 50/60 Hz |
| Mains fuse | 10 A, type C |
| TIG and MMA current range | from 5 to 250 A |
| TIG duty cycle 40°C | 150 A at 100%, 190 A at 60%, 250 A at 35% |
| Fast pulse | from 25 to 523 Hz, base current from 10 to 90% |
| Conventional pulse | pulse and pause from 0.01 to 10 s |
| TIG-A-TACK | from 0.01 to 2.50 s |
| Programs | 10 TIG and 10 MMA |
| Mains current | 7.1 A RMS, 13.0 A maximum |
| Mains power | 4.9 kVA at 100%, maximum 9.0 kVA |
| Open circuit voltage | 95 V |
| Efficiency and power factor | 87% and 0.94 |
| IP rating | IP23, S mark |
| Minimum generator size | 13.5 kVA with electronic voltage regulation |
| Source dimensions (L x W x H) | 520 x 220 x 360 mm |
| Source weight | 23 kg |
| Torch cooling | liquid, cooling module included |
What you get
- Migatronic Pi 250 DC power source with TIG DC HP panel
- liquid cooling module
- trolley
- TIG torch, 4 m long
- earth cable, 4 m long
What to watch out for
For continuous work count on 150 A at 40°C, as stated in the Migatronic manuals. 250 A is the current at 35% duty cycle.
This is the DC version, so for TIG welding of aluminium you need an AC/DC welder. The electrode holder for MMA is not included in the set. The housing has signs of use visible in the photos.
Questions about the Migatronic Pi 250 DC HP
Can the Migatronic Pi 250 DC weld aluminium?
In practice, TIG welding of aluminium is done with alternating current, and this is the DC version. For aluminium choose a TIG AC/DC welder, for example the ESS Squarearc 276C or the ESS Squarearc 356C from our used machines section.
How does the Pi 250 DC HP differ from the Pi 250 AC/DC?
The Pi 250 AC/DC additionally has alternating current for aluminium, with AC balance and frequency control. DC HP welds with direct current only, and this unit has fast pulse up to 523 Hz, Synergy PLUS and TIG-A-TACK.
Can I connect it to an ordinary three-phase socket?
Yes. It runs on 3 x 400 V mains, draws at most 13.0 A and needs a 10 A fuse, so a CEE 16 A socket is enough with margin to spare.
Will it run from a generator?
Yes, from a generator of at least 13.5 kVA with electronic voltage regulation. That is how Migatronic calculates it: 1.5 times the maximum consumption of 9.0 kVA.
What work is it most useful for?
Thin-walled stainless steel: pipes and pipework, tanks, railings, parts for the food industry. That is where fast pulse, low heat input and clean TIG-A-TACK tacks count.
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.
