Getting 120v Single Phase from 3 Phase


snip----
I fully agree, but I have no motors that can be strapped for 208. As I said, my Bridgeport is wound for 230. I don't recall what the Graziano demands, and the motor is internal--not readily available. I just know that it runs well on 240, so why risk anything? The induction furnace is wired 220/440. It would be within range, but the huge amperage demand makes running at a slightly higher voltage an advantage over running lower. Not necessarily for wire size, but, again, for heat control.

I understand that, but the cooler operation is certainly a benefit.

No, what I'm assuming is that the majority of the machines would be running in the tolerance zone, unnecessarily. Given a choice, why would I want any of my machines to run under voltage? Even within tolerance? Over voltage is far superior to under voltage if one must deviate from the ideal.

Could be, but I'd not be willing to gamble on it. Good example is the induction furnace, although it's not one of the machines that falls out of the tolerance zone (220/440 in this case). The motor generator weighs almost three tons, and is water cooled, not fan cooled. That means it has the potential to run hotter than I would like because it relies on heat conduction with small coils of circulating water wrapped around the exterior of the assembly. Adding any unnecessary heat to its operation would not be in my best interest, especially if it had the potential for failure. I can't speak for you, but I couldn't afford to pay for a rewind on something of that magnitude.

his
of
I
ago.
Dunno. As I said, I don't recall, but he has since built his own place and has it wired according to his needs. Can't help but think it's delta, but I couldn't swear it is. For all I know, he may be wired 480. I'll try to remember to ask him the next time we talk on the phone.

All well and good if you choose to use a wye service, but I chose to eliminate that problem. I'm as happy as if I had good sense. Even *if* one can get around the licensed electrician, you still face the cost of the buck/boost transformers, which, at a minimum, would cost at least $300 per machine, assuming you could get away with two instead of three. You also have the cost of mounting them, and the inconvenience of them being in place, adding considerably to the bulk of the machine, with no benefits. No thanks.

moment
my
where
load
lights
use
Nope! Wrong again. I am paying for two services in spite of my choice of delta over wye. *ANY* 3 phase service is considered industrial where we live. Had I run everything through the CT can, avoiding the meter base, I'd be paying for my power at a higher rate because I'd exceed the maximum (demand meter). Our meter base is a 375 amp unit, so we feed both the shop and the house from it, at a residential rate. It's simple------if I wanted three phase service, and I did, I had to pay for two services, like it or not (and I don't). As much as I may not like the cost, I'm very happy to have the convenience. I explored the idea of phase converters and quickly dismissed the idea. Way too expensive, considering the load I had with the induction furnace. I had two choices had I chosen phase converters-----buy one huge unit and pay for the idling current endlessly, or buy a few small units and bring them online as needed, still paying for idling current. It was cheaper, and far more convenient, to pay for three phase service.
To the best of my knowledge, I chose the right service for my needs. Considering I have nothing that is wired for 208, nor can any of it be rewired to accommodate that voltage, I sure as hell didn't want it in the shop. If industry today is headed that direction, and machine tools are so wired, that's a whole different situation, and I'd have no quarrel with the choice. With the machines I have, that wasn't one of the options, and I sure as hell wasn't going to spring for transformers that weren't necessary, not when all I had to do is request the right service.

Again, a judgment call. I have one device with that load. Why would I pay for 480 service, add an additional panel, then transform for everything else? Personally, I think I made some excellent choices. Everything I have runs as it should, and I haven't filled the shop with unnecessary transformers. Idling current alone would have been expensive in the long haul had I chosen that path. I have only one machine that *requires* 480 volts, a German made universal cylindrical grinder, which cannot be strapped for 240 volts, or anything within reason. The only time the transformer will be energized is when I use the machine. There will be no idling consumption otherwise, so I won't be paying for making heat. Regardless of your opinion, I feel I've done a damned good job of addressing the problems at hand. Your bias against delta service seems to be a much greater stumbling block for you than my choices are for me. Very strange, Pete. However, I think if you visited my shop and observed how nicely it all has come together, I think you might find yourself agreeing that I did the right thing. :-)
Harold
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Harold and Susan Vordos wrote:

<snip>
Interesting. In my former area commercial rates were lower per KWH than residential rates. As long as you could manage your loads well enough to avoid problems due to peak metering you could get better rates by hanging your house off of your commercial service.
That induction furnace of yours seems to be the biggest issue no mater which way you go. Such a massive single load makes it difficult to optimize for peak metering.
As for phase converters, for manual machines I'd use inverter drives instead since their costs have become quite reasonable and they don't have an idle current issue.
For CNC machines in many cases you could modify them to run from mostly single phase power and a smaller inverter or rotary phase converter. Not real practical for multiple machines in a larger shop, but a workable route for a couple machines in a home shop.

It's likely that the potential issues diminish as the equipment gets newer.

If you've only got one huge load then 480 service is probably not worthwhile.
Stepping up for the one problem grinder makes sense, just as adding boost transformers makes sense if it's only a machine or two that need them.
Remember, I'm not biased against delta service, I'm biased against wild leg delta service, two different things.
I'm sure your shop is quite nice, it sounds like it's well equipped.
Were I planning a new shop with the full list of equipment to be in it, their specs, etc. I might well decide on a service configuration that included delta service for the machines. I would just avoid a service configuration that included a wild leg.
Pete C.
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s

snip---
the
are
with
and
I certainly get that idea-----even PUD was somewhat surprised that I wanted the delta service.

I don't agree on the boost transformers, not when I'm as pleased as I am to have the service I have. As I stated, I don't consider buying boost transformers to be a bargain, nor would I like feeding them on a continual basis, in spite of the fact that we pay only $.0445 kwh for our power. I have yet to discover one thing about my service that displeases me, and I've had 3 phase delta since 1967. One of us is nuts! :-)

You keep saying that, as if there's other types. I've heard of a corner grounded delta (but don't understand how it relates to voltage), but as far as I know, they all have a wild leg if you shoot for 120V. Is there something I don't know or understand? The moment you introduce the neutral, seems to me you're bound to have only two phases that yield 120V unless your wired wye.

OK---fill me in, then. What type of service would it be? Strictly 240 V? That's what I have now. I do *not* use my 3 phase for single phase service*, although when I wire my mill permanently, I will have single phase for the power feed and work light, but only there. I'll do that so I can keep the wires away from the bottom of the machine. I have the box overhead, almost directly over the motor on the mill. 12' ceiling. You can do that when you have a 5 wire system. Everything else is strictly 3 wires, plus ground. Do you still have heartburn over my wiring?
*The same phases that constitute my A & C phases in the 3 phase panel feed my single phase panel, although through separate lines and conduit, from the pole. Want to see a pic?
Harold
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Harold and Susan Vordos wrote:

A pure delta service does not have a neutral at all. There is no 120v on it, only 240v phase to phase. The corner ground is strictly for safety purposes to limit the relative voltage from any phase to ground. This can make that phase look superficially like a neutral, but it is not.

How are you going to wire the mill? Separate conduit from each panel to separate boxes overhead and separate drops to the mill head and the light / power feed? Is the neutral present in your three phase panel so you can do a single feed from there? You can't or at least shouldn't (I'd have to look in the code book) combine circuits fed from separate breakers in separate panels in a single conduit run to the mill.
For the mill I would likely feed it strictly three phase and locally derive the 120v with a small transformer. Of course I got about a dozen 1 KVA 240/480 x 120/240 transformers for about $10 each brand new so that biases the economics a bit.
Pete C.
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corner
far
120V
OK, that makes sense. From what you're saying, then, is that you don't object to delta so long as you don't derive any 120V from it aside from transforming. For all practical purposes, that's what I'm doing this time, using my delta service only for 3 phase, with all (except one place) of the 120V stuff coming from my single phase panel, which I would have done anyway, due to the demand meter. However, using the delta service for 120V is done routinely, as you likely know. The only real disadvantage I am aware of is the lost space in the panel---the B phase, the wild leg. Byond that, I don't see any issues. As far as I'm concerned, changing to 208 volts is a greater sacrifice than losing the few spaces, at least with the equipment I own.

it,
V?
phase
can
You
3
As I said, my 3 phase service is 5 wire, meaning it is capable of delivering 120V single phase, per code. In the case of the mill, I'll take advantage of that and use the neutral, tapping either the A or C phase for the 120V. I have two boxes, side by side, coupled with a short nipple. One will have the three phase outlet for the mill, the other will have the single phase 120V, all fed from the same breaker, in the same conduit. It's clean and easy. Remember, we're dealing with only a few amps, tops. I'm not concerned about balancing the load in this case.

Chuckle! Put one of them in the mail to me and I'll wire it that way, so you won't worry about me and my safety! :-)
Harold
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Harold and Susan Vordos wrote:

Actually now that I think about it I believe they were marked at $10 and I got them for about $8 'cause I took the whole lot. I'm pretty sure the cost to ship one of those heavy little buggers across the country would far exceed what I paid for them although it would be much less than the $150 they seem to list for.
Pete C.
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Wrong. If it is a grounded (not grounding) circuit conductor, it IS a neutral, by definition. jk
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Harold and Susan Vordos wrote:

A pure delta service does not have a neutral at all. There is no 120v on it, only 240v phase to phase. The corner ground is strictly for safety purposes to limit the relative voltage from any phase to ground. This can make that phase look superficially like a neutral, but it is not.

How are you going to wire the mill? Separate conduit from each panel to separate boxes overhead and separate drops to the mill head and the light / power feed? Is the neutral present in your three phase panel so you can do a single feed from there? You can't or at least shouldn't (I'd have to look in the code book) combine circuits fed from separate breakers in separate panels in a single conduit run to the mill.
For the mill I would likely feed it strictly three phase and locally derive the 120v with a small transformer. Of course I got about a dozen 1 KVA 240/480 x 120/240 transformers for about $10 each brand new so that biases the economics a bit.
Pete C.
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Harold and Susan Vordos wrote:

A pure delta service does not have a neutral at all. There is no 120v on it, only 240v phase to phase. The corner ground is strictly for safety purposes to limit the relative voltage from any phase to ground. This can make that phase look superficially like a neutral, but it is not.

How are you going to wire the mill? Separate conduit from each panel to separate boxes overhead and separate drops to the mill head and the light / power feed? Is the neutral present in your three phase panel so you can do a single feed from there? You can't or at least shouldn't (I'd have to look in the code book) combine circuits fed from separate breakers in separate panels in a single conduit run to the mill.
For the mill I would likely feed it strictly three phase and locally derive the 120v with a small transformer. Of course I got about a dozen 1 KVA 240/480 x 120/240 transformers for about $10 each brand new so that biases the economics a bit.
Pete C.
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Harold and Susan Vordos wrote:

A pure delta service does not have a neutral at all. There is no 120v on it, only 240v phase to phase. The corner ground is strictly for safety purposes to limit the relative voltage from any phase to ground. This can make that phase look superficially like a neutral, but it is not.

How are you going to wire the mill? Separate conduit from each panel to separate boxes overhead and separate drops to the mill head and the light / power feed? Is the neutral present in your three phase panel so you can do a single feed from there? You can't or at least shouldn't (I'd have to look in the code book) combine circuits fed from separate breakers in separate panels in a single conduit run to the mill.
For the mill I would likely feed it strictly three phase and locally derive the 120v with a small transformer. Of course I got about a dozen 1 KVA 240/480 x 120/240 transformers for about $10 each brand new so that biases the economics a bit.
Pete C.
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Sorry 'bout all the dupes, had a little news server issue.
Pete C.
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everything
have
strapped
transformer
of
problems
right
Well since you are already running a separate service for the single phase, the 480 would have been the best for you. You don't need any transformers for the 480 service and you haven't mentioned any 3 phase equipment that requires 240 volts only. Also if you really have 75 amps of florescent lights (That's TONS of amps for lighting. Do you use sun glasses in side?? :-) you could have run all that from a 20 amp 277 breaker if you had a 480 wye setup! Much cheaper for the wire on the 50kw load on the furnace and smaller contactors and stuff on all other wires too....
William....

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I
long
480
Regardless
Pete.
has
phase,
side??
Yeah, but one fly in the ointment. I own a 23 KW heat treat furnace that is wired 208 volts, with a control transformer that has taps for other voltages. According to McEngelvan, I can simply change the lead for controls and get better service, considering the coils are actually rated for 240 volts. I have yet to do it because it's not set up at this point in time. The size of the transformer for something that large would have been somewhat discouraging for me, although I think that all my equipment, otherwise, could be wired for 460/480 volts. I had to make a decision, and feel that, considering I'm not well versed in electricity, I had to do what was most comfortable for me, which would be to work with a voltage that I had worked before. I think, under the circumstances, I made the right decision, although the 400 amp Square D (disconnect) switch for the induction furnace wasn't cheap at just over $600. I still have to buy the fuses. The shop isn't fully functional at this point due to our living in it while we're building our house. No need to set up things that I can't use at the moment.
Harold
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mandatory.
machines
store
it's
delta
It's the power co that saves on the transformers, not you. You get to supply the buck/boost transformers if you want them! Also the buck/boost transformers are on your side it the meter so you get to pay to keep them warm ( this is not as bad as keeping the big ones hot though)
William....
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snip--

Yep, which is just one more reason to avoid them if possible. I did!!
Harold
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Actually, in this instance, I paid for the transformers as a part of the cost of having the service installed. It had nothing to do with my decision to use a delta service, however.
Strangely, in Utah, my second service, which was three phase delta to our house, the power company started off playing hardball with me. They said the cost would be prohibitive, if they would supply it, but they wouldn't. Having already been through something similar with them once before, I very calmly explained to the clerk that if I didn't get satisfaction, my next stop would be the public services commission, where I'd file a complaint against the company. At that time (and perhaps still) they were a monopoly, and were bound to provide that which the customer needed. Interestingly, it suddenly went from "you can't have it, but it would be expensive if you could" to "no problem, and we can probably provide it free of charge, providing you sign a contract that guarantees a specific amount of use". It ended up costing us nothing to have it installed. It was also 3 phase delta, 240 volts. They had to install two poles, and, naturally, three transformers. It was not an open delta.
Harold
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my
Well there are disadvantages from the 208 voltage, a lot of motors will not run at 208 with out overheating them. And my band was blade welder didn't really like it either, had problems welding the larger blades. The oven elements also don't seem to get as hot, cloths dryer, etc.....
William...
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Buck/boost transformer.
Jim
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at
not
Exactly! I'm still at a loss to understand why the delta system is such a problem. Seems to me the Wye system, *for a machine shop*, would be far more disadvantageous. You'd have to be completely out of your mind to request it if delta was available.
Harold
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Harold and Susan Vordos wrote:

You're right, Harold. I think the 3 transformer delta service is the better of the two. One advantage is that when one transformer goes out a trouble shooter from the power company (me) can go out and rebuss it into an open delta and have you back up and running in 30 minutes. The two transformer open delta is only good for 86.6% of the KVA rating of the two transformers. So you might have to shed some load. :)
Don
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