Which 3 phase Voltage to get?

Hi all,
I would like some help / advice in outfitting my shop.
For the first time in my metalworking home shop, I am able to get 3
phase service from the local power company.
In the past, I have always used a 3 phase rotary converter that I built with the help of the group here - special thanks to Fitch and Bob Campbell.
My question is, which voltage should I specify - and why?
I can get 208v, 220v or 440v.
What are the pros and cons, if any, between the choices?
My lights and shop equipment are all multi-tap wired and are capable on running on any of the voltages.
I do have some small bench top and hand held machines that require 110v single phase.
I have one lathe powered by a 200v three phase motor - I would be willing to replace this motor, if it would seem to be an advantage to go with one of the higher voltages for other reasons.
I have hopes of going to some newer machinery in the future, most / all of it seems to be rated for 220v, but with the notation that it is operable on 208.
Your help and advice on this is greatly appreciated. Thanks in advance,
Jess
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Jess wrote:

If it's just a home shop do not get 440v. You're out of the realm of do-it-yourself electrical work and accidents involving 440 are *not* fun.

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wrote:

Brrrrrrrrr...no...440 is into the "fiery plasma ball exploding flaming bits of molten metal in a grenade like sphere of hell" sort of thing.
220 would be cool.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
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Uh 220, and even 120 will do that as well. It's not the voltage. but the available current. jk
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True..but how often have you seen 220 do that with a carbon track on a plug?
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
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Just as often as I have seen it happen on 480.
jk
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I guess I must be unusual then.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
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jk wrote:

I've seen it plenty of times on 480, can't remember ever seeing it on 240.
John
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wrote:

That makes sense to me. It's absurd to assume that the voltage makes no difference. Given a high enough voltage, an arc can generate when there are no proper conductors in the path. After all, aren't most insulators, for the most part, simply not good conductors? With enough pressure (voltage) anything will conduct------even glass. That being the case, it stands to reason that as the voltage is lowered, so is the propensity for arcing.
Harold
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Yep - the car battery does it nicely.
Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
Harold and Susan Vordos wrote:

-
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Tue, 13 Sep 2005 05:21:52 GMT in rec.crafts.metalworking :

    So, like, you're saying I should let my brother-in-law make any adjustments?

    When I was younger, I lived in Madrid, and in the new apartment, we were getting a step-down transformer installed to convert the local (220 volts) to American appliance (110 VAC). Heard the "zot" and kind of saw the flash of the short, definitely saw the electrician fall on his butt from the shock. He wasn't too hurt, but he utter those immortal words to live by:     "I didn't think that was going to work."
    Word.
tschus pyotr
--
pyotr filipivich.
as an explaination for the decline in the US's tech edge, James
  Click to see the full signature.
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My shop is wired 415V 3 phase. Did it all myself with an inspection by the electrical contractor before the sub board was 'hot'. Can't see it'll kill you any deader than lower voltages. I did it all to code because *I* was the one going to be using it.
Then again my single phase supply here in Aus is 240V, so I think our general wiring standards are waaay tighter than yours. When I lived in the USA a few years ago, at least, the general wiring standard, frankly, sucked.
Get the supply you think is going to be most useful for the size motors etc you're going to be running and do it to or above code requirements.
PDW
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Peter Wiley wrote:

First of all, I'm no expert and I'll certainly defer to the pro electricians in the group.
That said, 440/480 is uniquely dangerous in it's ability to sustain a plasma fire without tripping upstream breakers. A screwdriver dropped onto busbars can evolve into something that will burn your arm off or worse.
I think the electrocution risk is substantially greater than 240V as well.

Part of the problem is that standards enforcement is primarily a local issue. I agree that stuff like using a clothes dryer ground lead to pull current for the motor or lamp is pretty much nonsense.
I wired my garage subpanel myself as well. When I call the city inspector to sign it off, he said "You must have done it yourself, it's too neat for an electrician.

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I suspect the 440 you're referring to is a different animal, then. Our 415 3 phase is pretty common, used a lot for domestic air conditioners and the like. Country places off 3 phase are the only sites I've ever come across with 480V and it's single phase, not 3.

Heh. That's exactly what the inspector said to me when he checked my last place. It doesn't take *that* much longer to do it neatly than sloppily.
PDW
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Not so at all

So can 25V if you work it right, but 440/480 is no worse that 240 for sustaining a phase to phase arc.

jk
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wrote:

I think the previous statement is likely correct. Given adequate current supply, voltage determines arcing ability. I don't know if 440 is the magic number, but certainly the higher the voltage, the more likely this ability becomes.

440 is worse for everything safety-wise. P=I^R=E^2/R, so the power capacity of higher voltage is quite significantly higher. But higher voltage also lowers power losses in wire, increasing motor efficiency. Which is why it's used in heavy duty applications. I've seen 208 in a shorted 3 ph plug sear the skin off a whole palm of a hand; imagine 440!

Proly 4x as great. ------------------ Mr. P.V.'d, formerly Droll Troll

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The generally considered (such that there is one) "Magic number" is 100 V to sustain an arc in air.
400 some odd volts is in no way "uniquely dangerous". Yes it is more dangerous than 200 some odd, and less so than 600 some odd or 4160.

Only if you ASSUME that the available fault current is the same, which in general it is not.

That is based solely on arc currents, distance and exposure time, and the chances are better (if not good) that you have a current limiting device upstream at 440.

Probably and provably not. Far and away the greatest number of electrocutions occurs from 120 V circuits in the US. Yes the higher voltage can punch through the skin barrier easier, but far more people treat 120 in a very cavalier fashion. jk
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On Thu, 15 Sep 2005 18:16:45 -0700, jk wrote:

Wouldn't it also be a factor that 120 volts is much more commonly available (and especially around those without much knowledge of electricity) than 480 volts?
Since I'm posting on the subject of 3 phase power from the utility co. I'm curious if 3 phase power is more or less expensive per kilowatt hour than single phase. Is it even a valid comparison?
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Absolutely
It depends entirely on your rate schedule. Either could be cheaper. I have two services, I pay significantly less per kwh for one, than I do for the other, even though both are 120/240 100A services.
jk
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Actually, the open circuit voltage in arc welders is about 80V, and the voltage at sustainable arc is about 25V, iirc. There is no strict magic number, because arcing ability is highly dependent on geomety, w/ sharp points arcing much more easily than flat surfaces--ie, higher electric field intensity at cusps.
The salient point is, the higher the voltage, the more arcing you can have.
If you're going to throw in the upstream safety devices w/ 440, you're changing the game. Majority of electrocutions at 120V?? Mebbe cuz 300,000,000 people have 120V wall outlets??
*Per capita*, proly by far the greatest number of electrocutions occur in TV repairmen, at least back in the day when TVs were fixable (tubes, donchaknow). 10,000 V. Oh yeah, and high-tension linemen. ---------------------------- Mr. P.V.'d formerly Droll Troll
wrote:

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