If anyone is familiar with 3PH transformers and the proper connections please email me. I have more details.

Thanks,
Dave
dave@tigerelectrical.com

I'm not receiving PMs correctly, please email me.

Thanks,
Dave

A lot of us here are familiar with them; what's your question?

Check out the Theory section on the ECN Electrical Forum.

I broke down and read the instructions that came with the transformers. I was surprised by a few things...that when adjusting voltage slightly you can exceed the nameplate rating of the transformers, the 14 ga primary wires, and the 16/32V secondary.

Thanks,
Dave

It sounds like you are working with "buck-boost" transformers (120/240V to 16/32V) that you will be connecting into an open delta arrangement to go between 208 and 236V.

What is your question?

I am working with buck/boost transformers. I guess I was expecting the secondary to be 208V and the wire ga to be 6ga. You're correct...it's connecting to an open delta aiming for 208-220V. My basic questions were answered by the instructions. Understanding how it works is another matter. My one remaining question is...does it matter where the 208V leg is connected, or are they interchangeable?

Thanks,
Dave

https://www.electrical-contractor.n...Forum/15/topic/000066/Number/0/site_id/1

The above link is for connecting 2 low voltage secondary buck/boost transformers to change an 3 phase open delta input, to a higher voltage 3 phase output.


Are you trying to convert a center tapped 120/240 with a 208 "wild leg" 3 phase open delta, to a 120/208 wye?

Larry C

Ok, we're taking away your "American male" status.

A buck-boost transformer basically subtracts-adds the secondary voltage from-to the primary voltage. The low voltage is always connected to the H1 and H4 terminals and the high voltage to H1 and X4. The connection of the remaining terminals is dependent on your available-desired voltages.

Transformers work essentially the same way generators do- by using the principal that a moving a wire through a magnetic field will create curent. The more loops you put in the wire, the higher the voltage generated.

Only in a transformer, it's not the wire that moves, but the magnetic field- as current goes through the primary, a magnetic field is constantly built up and reversed in the transformer core, which in turn induced current in the transformer secondary. A buck/boost transformer has a number of taps on it, each of which is wired up to a different position along the coils, so that depending which tap you hook up to, there are more or less coils wrapped around that transformer core.

Thanks for your responses. The diagram was very helpful Scott. I see the 208 leg connects to the H1 of both transformers. The design is for a 3PH machine that requires 208V nominal. The existing voltage is 248 and I'm attempting to get to the upper range of 208-220V.

Dave