MID FREQUENCY WELDING is when inverted DC power is used for the welding. This is performed using a control and power supply system that takes and AC power input and converts it into an inverted higher frequency power output. AC 60 hertz goes in. It is inverted and converted a combination of times in the control and transformer to end up with a 400 – 4000 hertz inverted DC output.
Schematic Power Conversion In Control and Transformer of Mid Frequency Inverter
The weld current has no zero cross overs so it heats the part quickly. It is DC so there are no inductive power losses or problems with magnetic material in the machine throat.
Generally the plant power requirement is reduced substantially. Transformers can be reduced in size allowing better payloads for robot applications. Welds are fast in a few milliseconds.
Reference: ENTRON Controls LLC