single phase vs. 3 phase

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I'm looking to purchase a cabinet saw. I have 220 in my shop currently and plan on buying 220 machines when ever possible. While doing my research, I've heard people mention single phase and three phase power but without the benefits or limitations of each. Can anyone help me understand this a little bit more or point me in a direction? -mike
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I can think of two benefits of 3-phase - More HP in a smaller frame motor. Reduced electrical cost both in demand and KW.
Keep in mind that having 220 in your shop doesn't mean you have 3-phase available.
Erik

the
little
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Is there anyway to determine what I have short of having an electrician come out? Thanks for the responses. -mike

and
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You should be able to look at the consumption meter and see what it says also, you can call your utility co and ask them. If you have 3-Ph they will know.
Erik

research,
without
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come
Yes, real easy. 220 (actually 240v) is single phase. It would be real strange for a residence to have three phase. So, you have single phase.
Your question should be whether to use 240v or 120v.
If you have 240v in your shop, then you should use it. It simply works better; do a search and see what people say about it. If you don't have 240v, then 120v should be okay also.
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If he lives in Santa Clara, CA, the power is only 208. I used to have a business there, so I went with a 208V 3 phase 5HP motor on my compressor.
Wade Lippman wrote:

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Dave, the key word there is "business". It's *very* rare in the US to have 3-phase power in a residence.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
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guess I didn't make myself clear, Doug. I live in San Jose, but had a business in Santa Clara. The VOLTAGE is 208 in Santa Clara, as opposed to 220 (or thereabouts) in San Jose. NOW do you understand what I was getting at? I thought you'd understand my business was in an industrial area since I had 3 phase power!!!
dave
Doug Miller wrote:

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All of Santa Clara, or just industrial areas?
208v/120v is common in an industrial area.
http://www.dataforth.com/catalog/pdf/an110.pdf
Bay Area Dave wrote:

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that I don't know, since I was only concerned about the voltage in the shop I leased
dave
Rico wrote:

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Santa Clara doesn't have _a_ voltage. Power is brought into Santa Clara via high-tension transmission lines where the voltage is somewhere around 115,000 volts (115kv). It hits a substation where it is transformed to lower voltages for distribution (22kv is common in south san jose, for instance, although newer systems use higher voltages). The 22kv is then distributed to home, commercial and industrial users. The 22kv will be transformed to 240v (nominal) single-phase for home users, and typically 480v three phase for commercial (office parks et. al.) and higher voltages for industrial users. Commercial and industrial users have on-site transformers to produce various voltages for various purposes - 240/277/208 volt systems are quite common in commerical and industrial facilities - 277v is very efficient for flourescent lights while 240/208 is used for industrial purposes. 240 can be centertapped to ground to provide the common 120 (as is done by the grounded conductor at your home service entrance, for example). In all cases, the 22kv distribution will be three phase and where the commercial or industrial entity has its own transformer, the three phase will be distributed to the business. To save wiring costs, three phase isn't distributed typically within residential neighborhoods (past the 22kv stepdown transformer).
scott
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I was about to say that. :)
dave
Scott Lurndal wrote:

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An office I used to work in had 2 phases of 3 phase supplied to them, so they had 208v. It still isn't 3 phase, since they did not get the 3rd phase.
A factory I worked at had real 3 phase, so they used mainly 208v motors, though some of the big ones were true 3 phase.
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On Fri, 24 Oct 2003 15:58:47 GMT, spam snipped-for-privacy@milmac.com (Doug Miller) wrote:

I thought some of you guys had (domestic) heating that ran off it ?
Here in the UK it depends how your power is delivered. If it's underground (nearly everyone) then it's a serious spend to get 3 phase. If it's an overhead feed (just the rustics) then it's a lot cheaper as there's normally line-of-sight to a suitable transformer.
-- Die Gotterspammerung - Junkmail of the Gods
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(Doug Miller)

Normally, Three phase is not even in the neighborhood, so it is not an option, no matter the cost. I suppose they would string new lines, if you asked them, with a big checkbook!
--
Jim in NC



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We use single phase 120/240 with the 240 feeding large loads. It is derived from a single phase center tapped transformer. In fact you don't see 3 phase transformers until you get to very large industrial pad mounted units. The norm here (US) is a smaller single phase transformer hanging on the pole and serving 2-3 homes. If the 3 phases are available on the pole, usually only if you live on a main power route, it is possible to add one more transformer and provide "open vee" 3p delta with a centertap. That uses the existing service and adds the extra transformer to get the 3d phase. That arrangement isn't perfect 3 phase and can get some strange phase shifts with unbalanced loads between phase ab and bc but it does work, particularly if you are just feeding motor loads that balance out fairly well. For a bit more money they will add the 3d transformer and give you true 240v delta or, more common 208v wye with 3 120v to ground legs.
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On 25 Oct 2003 01:47:48 GMT, snipped-for-privacy@aol.comGreg (Gfretwell) wrote:

American electrics terrify me (a lot of your working practices are seen as screaming nightmares in our standards documents). And you do it in timber framed buildings too !
But I really don't understand how you can operate a system with such a mixture of 240 / 208 and 110 / 120 V systems. It must keep the motor-swap shops in business.
Here in Europe we just have single phase and three phase. Then barring the half-a-dozen different socket outlet styles, I can move any appliance around between _any_ two European countries and have it work, straight off. Standard voltage, right across the continent. Even dodgy old places like Spain and Greece are now getting their acts together (15 years ago I installed VFDs in a Spanish factory where we barely had a working phoneline)
-- Die Gotterspammerung - Junkmail of the Gods
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(Gfretwell) wrote:

240v
It is not a hard concept. You only make a mistake once! <g>
Really, the 110 plug will not fit in the 220, and also the other way around. If you don't understand it, don't play with it. A few do get it wrong, but not many.
It is nice to run 220 a greater distance, with lighter wires, and less voltage loss. You can't claim that as a disadvantage for us.
--
Jim in NC



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It is what happens when you invent something and never abandon any idea each inventor came up with. You folks were helped a lot by a war that destroyed enough of your infrastructure that you had to build it all back at one time, with uniform standards. We still have major utilities that date back to Thomas Edison. I have always said, the best thing we could have done was bomb all of our infrastructure to the ground in 1945 and build new stuff so we would be on equal footing with the rest of the world. In the long run we would have saved money.

Most commercial grade motors can be tapped for any of those voltages by swapping a couple wires in the bell.
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Gfretwell wrote:

Don't give Al Qaeda any ideas...
--
Michael McIntyre ---- Silvan < snipped-for-privacy@users.sourceforge.net>
Linux fanatic, and certified Geek; registered Linux user #243621
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