2 x 110V Control Transformers

[rngtech]

Hi all,

Client has requested that for PLC control panel instead of a single 110V control transformer, they would like to have two transformers in case one was to fail (even though this is highly unlikely). Ideally both transformers would be active (load sharing) and if one was to fail there would be no issues as the other one would still be functioning.

Is it fine to just put these in parallel with each other (transformers will be identical). I think there are redundancy modules but this would probably be more likely to fail than the transformers so don't really want to use one if them.

If anyone has any examples or point me to any drawings that would be great.

Thanks

 

[parky]

Yes I have seen it done, there are certain things that need to be adhered too,
The transformers exactly the same i.e.
The same primary & secondary voltage.
The same power rating.
The same impedence
Connected in the same phase

 

[BryanG]

I was going to make the sound of sucking air through my teeth, and maybe some tut tut sounds, but so much I know
https://electrical-engineering-portal.com/principles-of-transformers-in-parallel-connection-1
https://pressbooks.bccampus.ca/singlephasetransformers/chapter/paralleling-transformers/
I know that I would like some temperature sensing on the transformers and lots of fusing. And you have to think why/how transformers fail, sometimes they go open circuit but I have seen ones where there are shorts between winding in the transformer. In that case having a second transformer won't help and will actually make the fault worse.

 

[rngtech]

Yes I have seen it done, there are certain things that need to be adhered too,
The transformers exactly the same i.e.
The same primary & secondary voltage.
The same power rating.
The same impedence
Connected in the same phase

Thank you - Transformers are exactly the same.

 

[rngtech]

I was going to make the sound of sucking air through my teeth, and maybe some tut tut sounds, but so much I know
https://electrical-engineering-portal.com/principles-of-transformers-in-parallel-connection-1
https://pressbooks.bccampus.ca/singlephasetransformers/chapter/paralleling-transformers/
I know that I would like some temperature sensing on the transformers and lots of fusing. And you have to think why/how transformers fail, sometimes they go open circuit but I have seen ones where there are shorts between winding in the transformer. In that case having a second transformer won't help and will actually make the fault worse.

Thank you for the info.

That second URL was what I was reading through before posting so thanks for confirming. Much appreciated.

 

[cidchase]

What would be a good method of detecting the fault should one transformer fail? Current transducers?

 

[PreLC]

What would be a good method of detecting the fault should one transformer fail? Current transducers?

Probably a good idea to have AC current monitoring relays which will cut the input+Output of the transformers as soon as the voltage is out of spec.

Not sure what happens during(Dynamically) the failure of one of the transformers as the other one is intact.

 

[ABSLC500]

Not exactly what you are looking for, but we usually have a relay powered off of the primary 110v supply with the secondary supply on the NC of the relay. When the primary looses power, the relay contact closes and connects the secondary to the system.