# Wiring a Buck/Boost transformer for balanced line voltage



## lowcountrycamo (Dec 12, 2014)

I have a rotary phase converter to power a mill. This mill takes 220V +- %10. I am right on the edge at 244v per phase. Hence I havea Buck Boost transformer 240/120 pri 24/12 sec. Wiring this per manufacturers diagram it will drop voltage 24v from one line. Is it possible to wire so as to drop 12V from each leg? The image below recommends wiring like diagram 4. Thank you for any help or knowledge offered.


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## cabletie (Feb 12, 2011)

I am not sure why you even need the buck boost transformer. It seems you are in the range without it. If the mill needed 208 volts then I could see it.


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## AK_sparky (Aug 13, 2013)

Just add an extra 300' of supply conductor too it...The voltage drop should get you in range!


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## McClary’s Electrical (Feb 21, 2009)

Dude, you are not even considering nominal voltage. Trust me, I promise you , YOU DO NOT NEED TO REDUCE YOUR VOLTAGE. forget this buck boost nonsense


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## McClary’s Electrical (Feb 21, 2009)

AK_sparky said:


> Just add an extra 300' of supply conductor too it...The voltage drop should get you in range!


He's already in the range.


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## amigi968 (May 24, 2008)

Best guess from having used B/Bs at an old Kodak plant that had an insane tolerance of 117vac to 119 vac, diagram 3 should do it. Obviously, test the secondary before final installation. 
I understand many saying that he is already in tolerance, but I've been in the same situation where voltage was critical to be within a specific range.


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## oldtimer (Jun 10, 2010)

*B/B transformers .*

I have used B/B transformers to connect X Ray machines .

It was recommended by the manufacturer of the equipment , and never had any trouble !


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## Pfaffel (Dec 18, 2014)

In our underground workshop the line voltage can be between 230v-255v active to earth. We have never had an issue. Some mills will have a transformer to drop voltage for control circuits, so be mindful you might exceed the break over voltage of some passive components. But with the voltages you speak of, I wouldn't worry.


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## Sparkeee1978 (Dec 29, 2014)

For future installations, I am curious if a VFD would be something to consider? You can just do so much with them. They can handle odd voltages, and be used beneficially in upgrading the operation of a mill. Speed control, resistive dump for quick stops, high efficiency, things like that. Cost has come way down as well. Just a thought to throw into the mix.


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## Pfaffel (Dec 18, 2014)

Sparkeee1978 said:


> For future installations, I am curious if a VFD would be something to consider? You can just do so much with them. They can handle odd voltages, and be used beneficially in upgrading the operation of a mill. Speed control, resistive dump for quick stops, high efficiency, things like that. Cost has come way down as well. Just a thought to throw into the mix.



Most of the new mills do have a tiny VFD in them. A few hundred bucks is a lot cheaper then all the stuff you need for gear boxes.


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## Carultch (May 14, 2013)

cabletie said:


> I am not sure why you even need the buck boost transformer. It seems you are in the range without it. If the mill needed 208 volts then I could see it.


How exactly is he "in the range"?

It seems that his voltage is a couple volts over what is needed. Not really enough to affect the equipment, and certainly not enough to justify a buck/boost.

The equipment needs 220V +/- 10%. That means it can run anywhere from 198V to 242 Volts. 244 Volts exceeds the range by 2 Volts.


I don't think an extra 2 Volts will make a difference to a motor, if it is in the high direction. If it is in the low direction, it would be more of a problem.


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## OaklandElec (Jan 4, 2011)

I've got a a shop that has been having me install buck boost transformers on much of their equipment. Delta service, 220v on all on the name plates. Apparently the machine manufacturer says the run best below 220v. I've been hooking them up at 212v actual reading. I can't see the point but they keep paying me to do more...


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