MCCB Dilemma

Ask Schneider. Their telephone number is on their website.

It is an issue if you want 800V operation but not if you want 750V. But you have not given this essential fact!!

Offhand I can only think of 600 and 690V as standard voltages.

Check with Schneider, I think a rated voltage allows for normal tolerances of a supply.

To put in more directly, if you are USING it at a voltage of 750VAC or less, then no, it will not make one bit of difference. You didn't say what you are using it for...

Basically your operating voltage are either 380 or 440 volts. Changing the MCCB from rated insulated from 800 V to 750 V does not have any impact to it. You need to ensure that the existing MCCB rated Ampere and the KA are the same as the new unit. For the MCCB mounting holes make sure that they are the same dimension, otherwise you need to drill a new mounting holes.

You don't know the voltage, and maybe the OP doesn't, either.

Thanks

The breaking capacity for the various rated voltages are fine. I guess am worried about how likely a voltage 50v above my Ui(750v) is to occur. Any advice??

Your MCCB "Rated insulation voltage which is at 750V instead of 800V like the previous schneider." is the maximum voltage capacity that the MCCB can withstand before flash over between the phases inside the MCCB compartment if there is an voltage rise.

"Rated "insulation voltage (Ui) is the maximum voltage that the MCCB can resist. It is higher than the rated working voltage, in order to provide a margin of safety during field operation"

So are you USING it at 750VAC? I seriously doubt that, it's not a voltage used anywhere in the world.

So your worried about impulse or voltage spike events potentially causing damage to your MCCBs when running on a standard 3ph 400V, 480V or similar system.

An extra 50V either way is not much of a safety margin when voltage spikes are concerned, if you are concerned then you have to add surge or lightning protection not rely of the impulse voltage rating of the device as the primary method of protection, especially if the downstream connected electrical equipment also cannot handle the higher voltages.

Contact your local Schneider agent directly and ask them, it is likely they just redesigned their product range and that came out to be the new value (possible test standard revision) and it makes no difference to your selection process.