Transformer Use 1

[Newengkid]

Please see attached schematic for reference:

Question: A company designed a unit that's powered by two transformers (380VAC to 24VAC and the other 380VAC to 120VAC). There are three circuit breakers (CB1 60A, CB7 4A, and CB8 8A) which are positioned before the transformers.

The problem is CB7 and CB8 are tripping. Why? Also, we are told to use fuses if we wish to protect the transformers. What is the best practice? Do we need the circuit breakers before the transformers? What would be our best solution?

Thank you.

 

[MiketheEngineer]

Call the mfg??

 

[VEBill]

...CB7 and CB8 are tripping. Why?

Over current.

It's very difficult to troubleshoot over the Internet. The problem is presumably not shown on the schematic.

 

[waross]

The breakers are probably tripping on the transformer inrush. Inrush may be 25 times full load current.
There are code issues with selecting breakers to protect transformers. Call an expert in your jurisdiction.
PS. Protect the transformers with breakers on the secondary side.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[msquared48]

Or surge protectors?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com