The WT6000 inverter is an MFDC system (Mid Frequency to DC) is more elaborate than the SCR based Low Frequency Control System. From a three phase power supply, the control implements fullwave rectification. This rectified power is sustain with substantial capacitance in order to smooth out as much line ripple as possible.

There are four IGBT switches for controlling the output to the welding power transformer. The IGBTs are turned on and off in pairs (1 with 4, and 2 with 3).

Since IGBTs are turned ON and OFF by the control system, the algorithms for controlling the welding output are deterministic rather than predictive. The length of time that the IGBTs are left on (pulsewidth) determines the output to the welding transformer.

Using an inverter based system provides significant advantages for controlling welding current that is appropriate for welding various metals.

For steel, the requirements for resistance spot welding calls out for significantly lower welding current but over longer period of time as compared to welding aluminum parts.

In general, applications dealing with steel welding will require a "B" or "C" size inverter from WTC. The adaptive technologies that are suited for welding steel generally involve monitoring of the dynamic resistance curves as the welding nugget grows.

The requirements for welding aluminum calls out for significantly higher welding current over a much shorter period of time as compared to welding steel parts.

In general, applications dealing with welding aluminum will require a "D" or "E" size inverter from WTC. Adaptive and quality monitoring technologies that are suited for welding aluminum generally involve monitoring of electrode forces that can detect the formation of welding nuggets.

Also control technologies of rapid and precise current control are required for welding aluminum. This comes in the form of obtaining very quick rise time and producing repeatable quick current profiling during the growth of the welding nugget.

The advantages of inverter based controls with its deterministic current control algorithms lend its use for various applications for Projection, Seam and Butt welding systems.

The combinations of very quick current profiling abilities and quick adjustments that can happen in any lenght of current period. Projection welding of parts can happen if very short period of 20 milliseconds whereas butt welding for continuous rails for railroad lines occur in the period of minutes.

Inverter control systems can be configured for these wide ranging applications and many applications in between.