KEMPPI KMS 400 power source, used MIG/MAG welder

The Kemppi FastMig KMS 400 is an inverter direct current power source for MIG/MAG and MMA, with no built in wire drive. The duty cycle is 400 A at 36 V and 80% and 380 A at 33 V and 100%, the supply is 3 x 400 V with a 25 A slow blow fuse. The energy efficiency reaches 87% and the source weighs 35 kg.

What this machine is for

This is a base unit for multi shift work in heavy industry, in shipyards, on pipelines and on steel structures. A current of 400 A at an 80% cycle and 380 A at continuous work means the machine welds plate of large section with practically no breaks. The inverter runs at high frequency and holds a stable arc with mains swings from minus 15% to plus 20%, and the efficiency of 87% cuts the losses of active power against transformer designs of similar output.

The source has no wire feeder. For welding with wire you connect an external drive from the MXF series, that is the MXF 63, MXF 65 or MXF 67, or an ArcFeed suitcase feeder. Such a split lets you leave the heavy unit in a set place in the hall and put the light feeder next to the part. A fault in one module does not shut down the whole station, but you have to count in the cost of interconnection cables with the right current cross section.

The SuperSnake sub feeder extends the reach. An extra drive halfway along the cable works in a push pull system together with the feeder motor, so the wire runs without resistance and without deformation over a long distance, and the torch goes as far as 25 m from the central unit. That answers the assembly of large structures and work in the shipbuilding industry, where moving the source is awkward or unsafe.

The machine is multiprocess. In MIG/MAG it works on a constant voltage CV characteristic, in MMA it switches to a drooping CC characteristic that holds the set current whatever happens to the arc length. After the main welds you move on to repairs and tacking with a rutile or a basic electrode without bringing in a second source. There is no alternating current here, so you will not weld aluminium with a stick electrode.

Features and equipment

• Inverter with a high working frequency: efficiency of 87%, a stable arc with mains swings from minus 15% to plus 20% and lower energy use than in transformer machines.
• Multiprocess work: a constant voltage CV characteristic in MIG/MAG and a drooping CC one in MMA, switched from the panel.
• Modular build with no built in feeder: works with the MXF 63, MXF 65 and MXF 67 modules and with ArcFeed suitcase feeders.
• Support for the SuperSnake sub feeder: a push pull system stretches the reach of the torch by as much as 25 m from the central unit, without losing smooth wire feeding.
• Works with the FastCool 10 liquid cooling module: a three stage pump at 450 kPa and a 3 litre tank with a mixture of water and ethanol that does not freeze in an unheated hall. You switch the cooler on from the source menu and it starts together with the machine.
• Works with SFW panels with synergic lines: the wire feed speed is tied to the arc voltage, which shortens the setting up of the station and orders repeatability, also in braze welding with CuSi alloys.
• Arc dynamics control from minus 9 to plus 9: negative values soften the arc and damp the spatter, positive ones harden it and deepen the penetration, which matters when welding under pure CO2.
• 2T and 4T modes: two stroke for tacks, four stroke for long runs, with a crater filling phase and a final gas flow. Four stroke takes the load off the hand on welds several metres long, two stroke stays handier on short spots.
• Gas test and cold wire feed: you set the flow on the regulator and pull the wire through the package with no voltage on the contact tip.
• Gas preflow time from 0.0 to 9.9 s and postflow in automatic or manual mode up to 32 s: shielding of the pool at the start and while the crater freezes.
• Thermal and voltage protection: sensors watch the IGBT transistors and the rectifier bridges, and filters guard the boards against surges, which helps when working from a generating set.
• Ready for the processes of the Wise family, among them WiseRoot for root runs and WisePenetration for a steady depth of penetration: they let you weld without ceramic backings on an open groove with a changing gap.

Technical data

What to watch out for

The supply is 3 x 400 V at 50 or 60 Hz, with a tolerance from minus 15% to plus 20%, and the installation has to have 25 A slow blow fuses per phase for the machine to give the full 400 A. The rated power reaches 18.5 kVA and 19.5 kVA at maximum current. The working temperature range runs from minus 20 °C to plus 40 °C, so in a hot hall the thermal protection acts sooner. After it acts, leave the machine switched on, because the fans have to cool the power blocks.

Without a wire feeder the source does not work in MIG/MAG. The card does not list a feeder, a torch or interconnection cables, so ask about the equipment and about the cable cross sections, because it is they that set the real reach of the station. The shop catalogue data give gas cooling, while the maker documentation lists the optional FastCool 10 module, so confirm the configuration before you buy. With a liquid cooled torch you watch the fluid level, because a lack of flow stops the work.

The source weighs 35 kg with dimensions of 590 x 230 x 580 mm, so two people will carry it. The inverter needs blowing out from grinding dust now and then, otherwise the dust settles on the power blocks. The processes of the Wise family are optional software modules and often need to be activated by an approved service workshop, so do not assume they are loaded.

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.