208V 3PH to 460V 3PH

[Chasman]

Can someone smarter than me guide me on this.
Existing-two single phase transformers fed with 208V (212 actual) and needing460V 3PH to run an AC unit.
It has been operating for awhile, but had a power surge duting a generator test.
I am only getting 414V from the setup. I considered maybe a winding was open, but all are good.
Thank You

 

[rlundsrud]

Perhaps you could elaborate on your question. A drawing of the configuration you have would help.

 

[Sahib]

All are good.

Except,perhaps, the measuring instrumentation with the possibility of their electronics being affected by surge. So the voltage may be checked with a separate meter.

 

[Besoeker]

Can someone smarter than me guide me on this.
Existing-two single phase transformers fed with 208V (212 actual) and needing460V 3PH to run an AC unit.
It has been operating for awhile, but had a power surge duting a generator test.
I am only getting 414V from the setup. I considered maybe a winding was open, but all are good.
Thank You

Can you get to both ends of each generator winding independently of the others?

 

[GoldDigger]

Can someone smarter than me guide me on this.
Existing-two single phase transformers fed with 208V (212 actual) and needing460V 3PH to run an AC unit.
It has been operating for awhile, but had a power surge duting a generator test.
I am only getting 414V from the setup. I considered maybe a winding was open, but all are good.
Thank You

From your description of two single phase transformers at 208V, it sounds like you had a three phase open delta. This will cause each of the transformers and corresponding generator windings to supply more than 1/2 of the motor VA instead of just 1/3.
That could overload either or both transformers or interfere with voltage regulation and stable 120 degree phase shift at the outputs.
But if the problem remains after going back from generator to mains power it implies a permanent effect on one or both transformer, such as a turn to turn short.
You need to follow Besoeker's advice and isolate the two transformer outputs from the motor and each other to get useful information as quickly as possible.
If the output is an ungrounded open delta, voltage relationships can be weird while the motor is connected.

 

[kwired]

Can someone smarter than me guide me on this.
Existing-two single phase transformers fed with 208V (212 actual) and needing460V 3PH to run an AC unit.
It has been operating for awhile, but had a power surge duting a generator test.
I am only getting 414V from the setup. I considered maybe a winding was open, but all are good.
Thank You

If you are asking how you get three phase out of two transformers - it is probably connected in an open delta. Golddigger gave some more details on this.

Not sure what may have happened when your incident with the generator came up - these transformers wouldn't be easy targets for a surge to do much damage, in fact they pass such surges on through to the load pretty easily, so maybe you are not looking for a surge problem, at least at the transformer.

Sounds like the tranformers possibly may be 240 x 480 instead of 208 x 480, if so output voltage was low ever since initial installation.