How to Convert Floating Neutral to Grounded Neutral in Single Phase Supply

You are trying to use an inexpensive UPS in a way it was not intended to. Purchase a UPS with the proper specification and be glad that the MCB tripped and protected you from yourself.

Why cant you just connect your common line on the UPS to the ground line and run it that way? No transformers involved.

Why cant you just connect your common line on the UPS to the ground line and run it that way? No transformers involved.

I have two load, one which required floating supply and other grounded neutral. Earlier i was using two separate UPS both the load, but now my UPS with grounded neutral failed, so i was thinking to use first UPS for both.

Try this:

Disconnect EVERYTHING (UPS) from the power source.

Disconnect all wiring from the UPS to transformers, MCBs and any other interconnects.

Label each component, with schematic of connections, and place into the tote you have aquired for this purpose.

Then, later tonight, throw the tote into a garbage container.

Tomorrow, buy the proper UPS.

I believe your second pose (#4) answered the reason your CB tripped. You are taking a single device (likely sized for its defined load) and trying to support more load than it was designed to support.

Buy another UPS sized to support THAT system's load.

This wouldn't be a line interactive modified sine wave output UPS by any chance?

What type transformer do you have? Some have a neutral already bonded internally.If this is the case, and you ground the other phase, you will have a dead short.In this case, either do not bond the transformer or ground the opposite phase.

Thanks everybody.

My MCB was tripping due to charging current of transformer. So I increased MCB rating and now it is working perfectly.

This is not my field, but, I'll just remind you that you can continue to increase the rating of the MCB to compensate for trips, up until your house burns down.

Just a thought.

I have used two MCB, one of lower original rating and other higher rating. Higher rating MCB will be in line for initial 2 sec (for transformer charging current) and then it will disconnected from line and smaller rating MCB come in line.

That's a novel approach.

Is that covered somewhere in the NEC?

What is the output rating of your UPS, what size is the transformer and what are the sizes of the 2 breakers you have. Until we have #'s it's all speculation! Your approach of timming the breakers can work but it makes it more complicated.