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Modern welders
typically take the AC power from the input and convert it to DC
power through a rectifier to provide a DC voltage for welding.
A static
converter or a phase converting VFD should never be used for this
type of application. Doing so will almost certainly damage the
welder.
A rotary
converter can power a welder, but since the output of the welder is
adjustable for different welding conditions, the input power demand
will change accordingly. This creates voltage imbalance
problems for the rotary converter. Unbalanced voltage supplied
to
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a three-phase
rectifier can damage the rectifier, especially when it operates near
its capacity. The unbalance might also effect the consistency and
quality of the weld. Some welders also have a very poor power
factor on the input and when powered by a rotary converter, the
power factor on the input side of the phase converter will be
extremely poor, leading to overloading of the single-phase wire and
circuit breaker serving the load.
A digital phase
converter is the best phase converter for operating a modern welder.
The sine wave output of the converter is safe for powering a
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 rectifier
input, and the perfectly balanced voltage from
no load to full load ensure safe, smooth operation of the welder at all
times. Because a digital phase converter has electronic power
factor correction, it doesn’t make the power factor of the welder
worse, it actually corrects it to unity. This results in a very
efficient, utility friendly solution for providing three-phase power
to a welder.
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