Need 208V on 3 phases- presently only have a 208V Wild Leg

[Always4]

This is a first for me dealing with a 208V wild leg so this is why I’m coming here for help.

Problem:
I have a client that has a new piece of equipment that requires all 3 legs to be 208V, 240V leaves no margin for error since their motherboard is only rated for that voltage and a power surge could destroy it. So they are persistent that it needs to be 208V across all 3 phases. Can anyone advise as to how this can be accomplish?

The 3 phase service coming in has the following readings at the meter:

Phase to neutral
A 120
B 120
C 208

Phase to Phase
A-B 240
B-C 240
A-C 240

 

[roger]

You need to tell them they will need to purchase a correctly sized delta to wye transformer

 

[roger]

It can be achieved with a buck transformer but it would probably be as cheap doing it with a delta to wye.

 

[LarryFine]

You have a high-leg delta. Just to clarify, you need a 240v delta to 208v wye transformer.

 

[Joethemechanic]

their motherboard is only rated for that voltage and a power surge could destroy it.

The motherboard is rated 240 volts? What about the rest of the machine?

 

[Always4]

 

[Always4]

Thank you for the replies thus far. This is what was in the manual. I’m looking into a delta wye transformer but I can imagine it’s not going to be a quick turn around.

 

[Joethemechanic]

Thank you for the replies thus far. This is what was in the manual. I’m looking into a delta wye transformer but I can imagine it’s not going to be a quick turn around.

Well your transformer connection is this



What you need is this



Boost Buck Transformers may not work because the requirements call for a neutral. With the boost/buck setup the voltages in relation to your neutral are going to be way different. Your high leg will be 192 volts to neutral, and the other two will be 104 volts to neutral

 

[hillbilly1]

Since it calls for a neutral, definitely don’t want to buck/boost it. As others have said use a delta-wye transformer. These people are fast at getting a transformer out, I’ve bought several from them, and have been pleased.

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[don_resqcapt19]

Thank you for the replies thus far. This is what was in the manual. I’m looking into a delta wye transformer but I can imagine it’s not going to be a quick turn around.

You might be able to get three 5 KVA 240 to 120/240 transformers and wire them as a 3 phase 15 KVA delta/wye bank.

 

[Joethemechanic]

BTW, This is the type of machine it is

I got curious

 

[Jraef]

View attachment 2566397

I'd bet a dollar to a donut that it will be fine with 240V 3 phase. They (foreigners) don't understand all of our system configurations as they never see them, so they read somewhere that we have 480Y277 or 208Y120 and so that's what they put on their specs. Everything on there looks to be servo driven, so the servo amps will just be converting to DC anyway.

 

[zbang]

If there are no voltage setting switches, then 208 or 230 (or 240 or 400) won't matter. As it doesn't need a neutral for "3 x 230V 50Hz" it probably doesn't ever need the neutral.

They also specify that in the American market, each lead should be MTW, and I doubt you'll find flexible cable containing MTW. You will, of course, find 10/5 SO cable, which is what almost anyone would use in the USA.

(Time to ask the Summa what they really need.)