The ESAB LUA 400A is an industrial thyristor power source for multiprocess bays. You set the current steplessly from 20 to 400 A, at a 35% duty cycle the machine holds 400 A, and in continuous work 200 A. Once you complete it with equipment it works with the MMA, TIG and MIG/MAG methods, and the weight of 250 kg shows what class of components it is built from.
What this machine is for
This is a source for thick sections and mill products, where the current held for a long time counts, not a set of functions on a display. A thyristor bridge with a main transformer turns the mains voltage into a steady direct current and takes overloads and swings of the plant mains well. The maker pointed this model to heavy industry, steel structures, shipyards and machine shops, and the applications listed are load bearing parts of halls, repairs of hulls in dry docks, thick walled pipelines, reclamation of mining and construction machines, pressure vessels and examination bays in welder qualification centres. The power block holds the set current whatever happens in the switchgear, and with large loads started on the same installation that is a real difference in arc stability. The construction has few assemblies that can fail, and those it has can be serviced without changing whole modules. In return you get the weight, a higher draw from the mains and settings read off an analogue scale. This is a choice for a plant that wants a strong source working for years at one bay, not a machine to carry between sites.
The external characteristic switch changes the way the source works for the method you pick. The control circuits modify the open circuit voltage and the profile of the voltage drop, so the same machine feeds an MMA, a TIG or a MIG/MAG bay. A change of process needs the current cables to be moved by hand and the equipment to be matched, and for welding with wire a separate feeder is needed, for example the ESAB MED 304, together with an interconnection cable.
Pulse is a separate matter. The source itself has no pulse electronics, but on the front panel there is a multi pin socket for an external controller. Once you connect such a module the machine welds MIG/MAG with a pulsing current, that is it lifts the base current with peak values and carries the drops over without spatter. This mode makes sense on stainless steels and aluminium alloys, where the face and limiting the distortion of thin sheets count, but it needs ESAB control equipment.
Features and equipment
- Power block on a thyristor bridge with a main transformer: direct current of a stable value, resistant to voltage swings in the plant mains.
- Stepless current adjustment from 20 to 400 A with a potentiometer and a mechanical gear: you change the settings without jumps, exactly to the material thickness and the welding position.
- Duty cycle 400 A at 35% and 200 A at 100%: reserve for thick welds and a real current for work without breaks.
- External characteristic switch: one base handles MMA, TIG and MIG/MAG once you change the equipment.
- Anti-Freeze in MMA mode: on a short circuit of the electrode the circuit cuts the current, so the core does not glow and the electrode holder does not melt its contacts.
- Communication socket for an external pulse controller: once it is fitted you weld MIG/MAG with a pulsing arc.
- Forced cooling with an industrial fan: the air stream goes onto the heat sinks of the thyristor block and onto the transformer windings.
- Thermal sensors that cut off the welding circuit: on a risk of overheating the machine stops the work itself.
- Weight of 250 kg from solid transformer components: a construction meant for multi shift work, without fast wear of the power circuit.
- Work with covered electrodes of large diameters: at a current of 400 A you pull thick cores on multi layer structural joints.
- TIG striking once a torch with a gas valve is connected: direct current for high alloy steels and for root runs.
- Simple diagnostics and access to the assemblies: a thyristor circuit is serviced with components, not by changing whole modules, which matters in a machine planned for years of work.
- Work in a multi shift cycle: forced cooling together with thermal protection lets you keep the bay running through the whole shift.
Technical data
| Brand | ESAB |
|---|---|
| Type | thyristor power source |
| Mains supply | 400 V, 3 phases |
| Welding current range | from 20 to 400 A |
| Duty cycle 35% | 400 A |
| Duty cycle 100% | 200 A |
| Parameter adjustment | stepless |
| Processes handled | MMA, TIG, MIG/MAG |
| Net weight | 250 kg |
| Torch cooling | gas |
What to watch out for
The supply is 400 V in three phases, and the net weight is 250 kg, so unloading and moving it around the shop need a fork lift. A transformer construction draws more from the mains than an inverter of similar current and needs a solid connection. At 400 A the duty cycle is 35%, for work without breaks 200 A is left and you plan the output of the bay to that value. The ventilation ducts have to be blown out regularly, because grinding dust blocks the flow and raises the temperature of the power block, and then the thermal sensor cuts off the welding circuit in the middle of the work.
The source alone does not weld with wire: you need a feeder and an interconnection cable, and for pulse a separate controller, which the description does not list in the set. You read the settings off an analogue scale, without a digital display, so repeatability of the parameters rests on the notes of the operator, not on the memory of the machine. A change of method needs the current cables to be moved and the equipment changed, which takes a few minutes and needs room around the source. The product data sheet gives gas cooling of the torch, for a liquid cooled version a separate cooler is needed. Pick welding cables with a cross section for a current of the order of 400 A, because too thin a cable heats up and eats the voltage needed at the arc. With the MMA method and basic electrodes remember to dry the coating, because damp gets into the weld whatever the class of the source.
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.