Step up transformer needed

rbdjr59 · Dec 30, 2016

I have a mill wired for 440 3-ph. My service is 220 3-ph. I am looking for a step up transformer to run my mill. If anyone has one for sale, I am interested. I also would like to hear of any specific concerns I should be aware of in attempting something like this.

9100 · Dec 30, 2016

You can use either a three phase line transformer or either two single phase units in open delta or three in delta or wye. Such transformers are common. I have two 20 KVA and two 25 KVA ones that would work but shipping to Houston from St. Louis would be expensive. There must be a used electrical equipment dealer in your area. The first thing to do is see what type motor you have. Most can be changed between 240 and 480. If it can't, look at the full load power requirement of your machine so you know what size transformer you need.

johnoder · Dec 30, 2016

Have run a 1 1/2 HP four speed 460V only for 13 years on the new ACME 3 KVA three phase dry type general purpose transformer I bought at the time - wired up BACKWARDS to be step up - all recommended and sized by ACME

rbdjr59 · Dec 30, 2016

This is for my 3B-48 Devlieg Jig Mill which has several motors, some of which are hard to get at. Re-wiring the motors would be a major pain and I may want to run more than one machine on this power in the future, but probably not more than one machine at a time. John, it seems that the step down models are more available, at least on the used market, but I've read that all are not compatible with running in reverse. I need a little more knowledge in order to ask the right questions at the used equipment dealer.

motion guru · Dec 30, 2016

rbdjr59 said:
This is for my 3B-48 Devlieg Jig Mill which has several motors, some of which are hard to get at. Re-wiring the motors would be a major pain and I may want to run more than one machine on this power in the future, but probably not more than one machine at a time. John, it seems that the step down models are more available, at least on the used market, but I've read that all are not compatible with running in reverse. I need a little more knowledge in order to ask the right questions at the used equipment dealer.

I'd be interested in reading what you have read that indicates non-compatibility with running in reverse.

Milacron · Dec 30, 2016

You don't need a "step up" transformer...you just need a 3 phase transformer. If has input of 440, output of 220 you simply reverse that and your input wires connect to the 220 side.

Milacron · Dec 30, 2016

motion guru said:
I'd be interested in reading what you have read that indicates non-compatibility with running in reverse.

Yes, that is curious...I've done it hundreds of times over decades and never a problem. I've also never encountered a blown 3 phase transformer...no matter how dirty or ugly, they always work.

Monarchist · Dec 30, 2016

motion guru said:
I'd be interested in reading what you have read that indicates non-compatibility with running in reverse.

Rare, but not THAT rare, ones NOT recommended for reversal DO exist. Power 'conditioner' types & c. with attendant complifications of resonance & tuning, mostly. Engineering reasons have been covered right here on PM.

Otherwise, 99 44/100's % of the 'dry' type we see every day have reversibility on their maker's data sheets if not on the dataplate.

Modest efficiency hit, very minor voltage divergence from spec. No Big Deal. JFDI.

Bill

JST · Dec 30, 2016

It does generally work.

It is NOT approved by current electrical codes unless the maker says it is good. We had a discussion a while back that has the details.

Short version (a fwe items left out) is that

1) some transformers have the turns ratio adjusted to produce correct output under load as a stepdown, and this works doubly against you, giving a very low voltage as a step-up.

2) many step-down units are made with insulation on the secondary to ground that is not up to line transients, and has not been tested for breakdown.

if you avoid #1, then #2 does not have to bother you, unless, of course, you DO get one of the line transients that the unit is not able to withstand. Then it may fail with bad results.

But usually you get away with it fine. Someone in another thread said that ER doctors hear a lot of "I've been doing that for 50 years with no problems". And probably it is the same with failures in step-up service.

rbdjr59 · Dec 31, 2016

Good info here, thanks guys.

rbdjr59 · Jan 4, 2017

I bought a transformer and would,like for someone to tell me how I should wire it to get 440 or thereabouts coming out when I put 220 in.

rklopp · Jan 4, 2017

I need a bigger picture. That one is too fuzzy.

Monarchist · Jan 4, 2017

rbdjr59 said:
I bought a transformer and would,like for someone to tell me how I should wire it to get 440 or thereabouts coming out when I put 220 in. View attachment 187710

Given that it was wound for 208 Wye?

We need to know more about your "220" source.

You may not be quite finished with acquiring transformers.

rbdjr59 · Jan 4, 2017

The pictures from my iPad don't seem to turn out well when posted here. I've taken some with my digital camera and will post,them when I get home, from my desktop. What info do you need about my service. All I know is that I have 220 on the high leg and two legs of 120. I have pictures of my panel, meter, and the transformers hanging on the pole. All of this stuff has been here since the 70's through multiple tenants who were of the "git her done" school of work. It's not pretty but it works, kind of. What do y'all need to see?

Monarchist · Jan 4, 2017

rbdjr59 said:
The pictures from my iPad don't seem to turn out well when posted here. I've taken some with my digital camera and will post,them when I get home, from my desktop. What info do you need about my service. All I know is that I have 220 on the high leg and two legs of 120. I have pictures of my panel, meter, and the transformers hanging on the pole. All of this stuff has been here since the 70's through multiple tenants who were of the "git her done" school of work. It's not pretty but it works, kind of. What do y'all need to see?

No huhu. I have the transformer maker's pubs on disc arredy.

But ..

Post #1 you said your service was 220 V 3-Phase.

Your new transformer is THREE PHASE @ 208 VAC 'Wye' on the primary.

AND ....you've just described a 'nominal' 220 VAC single-phase, sometimes called 'split' phase service.

So.... Do you REALLY HAVE 3-Phase service? Or not?

Bill

Mud · Jan 4, 2017

motion guru said:
I'd be interested in reading what you have read that indicates non-compatibility with running in reverse.

Here's one thread that I know of - http://www.practicalmachinist.com/vb/transformers-phase-converters-and-vfd/how-can-machine-ground-affect-welding-arc-325892/?highlight=ground

The transformer works OK, but the ground safety is not correct.

rbdjr59 · Jan 5, 2017

Well Bill, I really don't know enough to make a indisputable statement about what my service is. I've always thought that there were a couple of different types (voltage wise) of 3-ph. but I don't claim to know much about 3-ph. Around here a service with one leg of 240 and two legs of 120 is often called low voltage 3-ph., correctly or not. It runs my 3-ph. motors and I thought it was compatible with what I am trying to do. Here are some pics of my service.

rbdjr59 · Jan 5, 2017

Here are some better pictures of the transformer placard, for those who don't have the factory schematic.

JST · Jan 5, 2017

Monarchist said:
No huhu. I have the transformer maker's pubs on disc arredy.

But ..

Post #1 you said your service was 220 V 3-Phase.

Your new transformer is THREE PHASE @ 208 VAC 'Wye' on the primary.

AND ....you've just described a 'nominal' 220 VAC single-phase, sometimes called 'split' phase service.

So.... Do you REALLY HAVE 3-Phase service? Or not?

Bill

He described 3phase "farm / lighting tap / wild leg" 3 phase. Perfectly good 3 phase, with a 120/240 single phase capability.

However, no taps on the 208 side. 208 is not 240 and transformer is not good for 240, which is over 10% high to start with, and can go another 10% higher.

The step-up needs to have a 240V not 208V winding.

Monarchist · Jan 5, 2017

rbdjr59 said:
It runs my 3-ph. motors and I thought it was compatible with what I am trying to do. Here are some pics of my service.View attachment 187760 View attachment 187761 View attachment 187762 View attachment 187763

Yes, it is 3-Phase. As to calling it "low voltage 3-Phase"? More confusing a term than useful.
And therein lies an issue. Too much 'name confusion', too few specifics so far in this thread.

You now have a 208 'Wye' to 4XX volt (MANY taps) transformer that is 'not quite' what you need.

220/230/240 'Delta' to 4XX 'Delta' with (at least) the basic "5%" taps wudda been the better fit (I have one - a 15 kVA)

Now - I *prefer* Wye where I have a trustworthy Neutral and predictable max above Neutral OR Earth on any given leg.

I am not as keen on corner-grounded, high-leg, 'stinger lead', 'floating', yadda, yadda .. Delta.

The load motors are happy so long as they get what they were wound and/or option-connected for.

Your issue, then is simpler.

A primary wound for 208 Volts that you are going to offer 220 to 240 Volts to.

When I said you may not be done buying transformers, I had in mind buck/boost single-phase units to tame that difference so you don't overheat the primary. Secondary winding is less of an issue. This transformer has taps enough to get 'close enough'.

ISTR we have a few PM members who are running just that sort of 230/208 solution, so I'll go and do something else for a while and hope they chime in with specifics that fit your need.

Simplest, of course, if you sell-on this transformer and go and get the correct one.

A primary for any of 220, 230, or 240 are close enough to your service to not matter. 208 is not.

Bill

Step up transformer needed

Cast Iron

Diamond

Diamond

Cast Iron

Diamond

Administrator

Administrator

Diamond

Diamond

Cast Iron

Cast Iron

Diamond

Diamond

Cast Iron

Diamond

Diamond

Cast Iron

Cast Iron

Diamond

Diamond

Similar threads