ESAB LTG 250 is an industrial thyristor power source for TIG welding on direct current and with a covered electrode. You set the current from 4 to 250 A, at a 35% duty cycle the machine gives the full 250 A, and the supply is 400 V in a three phase system.
What this machine is for
Thyristor control gives a soft arc characteristic, which helps in precise joining of thin parts in high alloy steels. The thyristor bridge holds a stable arc also when the mains voltage swings, and the lack of complex inverter electronics translates into service life in halls where metal swarf floats in the air.
Direct current covers carbon and stainless steels. You will not weld aluminium with this machine, because that needs an AC/DC power source. In MMA mode the power source pulls rutile and basic electrodes up to 5.0 mm, and it copes with cellulosic electrodes as well, the ones used in site work and on pipelines.
A power source like this works on process pipelines in acid resistant stainless steel, on installation assembly in the food and chemical industry, on repairs in boiler houses and heat and power plants, on tight pressure vessels and on stainless steel structures, for example railings and medical equipment. The manufacturer points to the power industry and to reconditioning workshops.
Features and equipment
- Thyristor technology with phase control of the current. The dynamics of change is lower than in an inverter, but the resistance to thermal overload is higher. The cost is a higher weight, because a classic main transformer works inside.
- HF ignition, that is an arc start without contact. The high frequency module ionises the shielding gas, so the tungsten electrode does not touch the material and there are no tungsten inclusions in the weld. This matters on pipelines examined by RT and UT methods. The ignition works surely also with long TIG torch cables.
- Lift ignition as a second option, that is a start by touching and lifting the electrode, useful where an HF module would disturb the electronics next to it.
- Current down slope adjustment, that is Slope Down. The arc dies away in a set time, so the crater at the end of the weld is filled and a pressure joint stays tight.
- MMA mode with the characteristic of a welding rectifier, for rutile, basic and cellulosic electrodes up to 5.0 mm.
- Forced fan cooling with a tunnel layout. The air stream goes straight onto the thyristor heat sinks, bypassing the control parts, which helps in dusty halls.
Technical data
| Brand | ESAB |
|---|---|
| Current type | DC |
| Welding methods | TIG DC, MMA |
| Supply | 400 V, three phases |
| Maximum welding current | 250 A |
| Current range | from 4 to 250 A |
| Duty cycle | 250 A at 35% |
| Arc ignition | HF without contact and Lift |
| Electrode diameters in MMA | up to 5.0 mm |
| Cooling | liquid according to the product record |
What to watch out for
The supply is 400 V in a three phase system, and the description does not give the fuse rating, so agree the connection with an electrician. The product record gives liquid cooling, while the maker description lists forced air cooling, with a duct that directs the stream onto the thyristor heat sinks, so pick the torch only after the configuration is confirmed: either for gas cooling or with a separate liquid module.
A thyristor build with a transformer weighs its own, so plan a fixed station and transport on a pallet, all the more since the description gives neither the weight nor the dimensions. The cycle of 250 A at 35% sets work at full current, on longer beads go lower. In a dusty hall keep the air flow clear and the heat sinks clean.
This unit is sold
This machine has already gone to a customer. Similar units are listed below, and if you want the same model, leave your contact details in the form and we will let you know when the next one arrives.