How to prove an MCB functions correctly?

It also depends what functions you wish to test - things like arc traps will be as good as the day they were fitted, likely age related failures are de-latching current due to worn mechanics or sticky lubrication, or overheating at steady load due to contact corosion.

If all you really need is some confidence it is not either stuck or too frisky, and will not overheat in normal use, then those factors can be tested with the right current but at a far lower voltage than the real event - an adjustable  variac plus transformer, to create a set-up  not dissimilar to an arc welder, capable of being set to various short circuit currents up to  a few hundred amps would be an approach.

A C50 should fire promptly at a current between 250 and 500A, and get warm but not dangerously hot after some tens of minutes at 50A.




To do it properly, i.e, break a real multi kA fault at full voltage is probably impractical.

It also depends what functions you wish to test - things like arc traps will be as good as the day they were fitted, likely age related failures are de-latching current due to worn mechanics or sticky lubrication, or overheating at steady load due to contact corosion.

If all you really need is some confidence it is not either stuck or too frisky, and will not overheat in normal use, then those factors can be tested with the right current but at a far lower voltage than the real event - an adjustable  variac plus transformer, to create a set-up  not dissimilar to an arc welder, capable of being set to various short circuit currents up to  a few hundred amps would be an approach.

A C50 should fire promptly at a current between 250 and 500A, and get warm but not dangerously hot after some tens of minutes at 50A.




To do it properly, i.e, break a real multi kA fault at full voltage is probably impractical.