A reader after reading the article:
What is the switching device in an inverter?
Asked how many times does the IGBT switch per second? The mid frequency direct current controls that dominate the resistance welding market operate at 1000Hz.
The IGBT’s are very fast and efficiently switch at a rate of 1000 times per second. There is an upslope as the current rises from zero to the desired level. On efficient systems this can be as fast as 3 milliseconds. This can be seen in the following diagram. There is a similar downslope.
Conversion In Control and Transformer of Mid Frequency Inverter
This diagram is more fully explained in the article:
The MFDC wave form diagram is not clear
Reference RWMA – Resistance Welding Manual 4th Edition