Current Injection to Test MCCBs

If you are just checking trip current, the voltage can be very low.

I often have to test MCBs for trip current, and the test set that I use consists of an old-fashioned arc welder transformer which is fed on the primary side from a 230V supply via a variac. The MCB is connected as a short-circuit load on the secondary side, and the current is measured with a clamp meter. With this setup I can test at up to 120A for short bursts, and up to ~100A sustained.

To test MCCBs you could build up a similar test set, but you will need more current, at least 2.5 times the rated current of the largest MCCB that you wish to test.