Buck/boost step up for MRI machine

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RustyNubbs

Member
Location
Denver
Occupation
Electrician
Hello,

Long time reader, first time poster.

I recently was asked to bid a job at an orthopedic office that is upgrading one of their MRI machines. The MRI machine instructions specifically states that the machine needs 30 amps at 240 volts. It is also supposed to plug into a NEMA L6-30R. The facility currently has 3 phase 208 volt power.

My question is this: Couldn’t I install a buck/boost step up transformer on the wall of the MRI room with a cord and plug that plugs into the L6-30R and then a cord and plug for the new piece of equipment?

I have a clear run from the electric room to the MRI room to get 208 volts. I also got a quote from Larson Electronics on a step up transformer that would work for my application. Plus, Larson said their buck/boost transformers are good for sensitive electronics.

Any and all information is greatly appreciated.

Thanks!
 
The issue with most buck boost arrangements is the Line-Neutral voltage also gets affected. If your load doesn't these are often less expensive.
 
curt swartz said:
Some equipment does not like the higher voltage to ground. I would verify with the manufacture before connecting it this way. Could be a very expensive oops.
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If he uses a buck/boost transformer there is will be not neutral involved. Just 1Ø, 208-1Ø, 240 volts.
 
infinity said:
If he uses a buck/boost transformer there is will be not neutral involved. Just 1Ø, 208-1Ø, 240 volts.
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Right, but you will end up with a boosted L whose voltage to ground will be 120V*(240/208) = 137V.

So if the equipment wants L-L to be 240V and L to G to be no more than 120V, that's a problem. For example, if the equipment has MOVs installed L-G as surge protection, is the higher L-G voltage a possible problem?

Cheers, Wayne
 
LarryFine said:
Unless the secondaries are split and each one tied to opposite ends of the primary.
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Thanks for reminding me that there are numerous configurations you could use to do this.

My previous computation of 240V / sqrt(3) = 139V (137V was a typo) assumes you boost each 120V leg relative to neutral separately, so I think you'd need two buck/boost transformers.

What you propose would make the L-G voltage 60*sqrt(5) = 134V.

And if you just boost one leg relative to the other, then one leg is 120V to ground, and the other ends up at 148V to ground.

Cheers, Wayne
 
I assume that the piece of equipment uses a resistive load due to the fact that there’s no neutral so a higher leg wouldn’t be an issue?
 
Being an expensive piece of equipment, it probably has surge protection, and like others have said, it probably won’t like it. It will be more expensive, but you will probably be better off using a 208 single phase to 240 single phase step up transformer.
 
hillbilly1 said:
Being an expensive piece of equipment, it probably has surge protection, and like others have said, it probably won’t like it. It will be more expensive, but you will probably be better off using a 208 single phase to 240 single phase step up transformer.
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I’ve been looking everywhere, but it seems like all step transformers have uneven legs.
 
Your supply house should be able to easily get you a transformer. Let them do the work. My primary supplier likes getting the non standard stock transformers from Hammond. Not sure of the smallest size general purpose transformers readily available in single phase 208 - 120/240. You might be stuck with the 15KVA.
 
Well thanks for everybody’s help. Much appreciated! I’m going to talk to the manufacturer after the holidays and hash it out.

Happy new years!
 
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