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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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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 |
#2
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Jess wrote:
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? 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. 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 |
#3
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In article , Jim Stewart
wrote: Jess wrote: 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? 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. 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:
In article , Jim Stewart wrote: Jess wrote: 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? 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. 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. 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. 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. 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. 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 |
#5
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In article , Jim Stewart
wrote: Peter Wiley wrote: In article , Jim Stewart wrote: Jess wrote: 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? 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. 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. 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. 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. 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. 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. 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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Jim Stewart wrote:
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. 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. Not so at all A screwdriver dropped onto busbars can evolve into something that will burn your arm off or worse. So can 25V if you work it right, but 440/480 is no worse that 240 for sustaining a phase to phase arc. I think the electrocution risk is substantially greater than 240V as well. PDW jk |
#7
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"jk" wrote in message ... Jim Stewart wrote: 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. 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. Not so at all 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. A screwdriver dropped onto busbars can evolve into something that will burn your arm off or worse. So can 25V if you work it right, but 440/480 is no worse that 240 for sustaining a phase to phase arc. 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! I think the electrocution risk is substantially greater than 240V as well. Proly 4x as great. ------------------ Mr. P.V.'d, formerly Droll Troll PDW jk |
#8
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On Mon, 12 Sep 2005 14:28:25 -0700, Jim Stewart
wrote: I can get 208v, 220v or 440v. What are the pros and cons, if any, between the choices? 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. 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 **** out of you for torturing the cat." Gunner |
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Gunner Asch 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. Uh 220, and even 120 will do that as well. It's not the voltage. but the available current. jk |
#10
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On Wed, 14 Sep 2005 17:44:13 -0700, jk wrote:
Gunner Asch 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. Uh 220, and even 120 will do that as well. It's not the voltage. but the available current. jk 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 **** out of you for torturing the cat." Gunner |
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Gunner wrote:
True..but how often have you seen 220 do that with a carbon track on a plug? Gunner Just as often as I have seen it happen on 480. jk |
#12
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Let the record show that Gunner Asch wrote back on
Tue, 13 Sep 2005 05:21:52 GMT in rec.crafts.metalworking : On Mon, 12 Sep 2005 14:28:25 -0700, Jim Stewart wrote: I can get 208v, 220v or 440v. What are the pros and cons, if any, between the choices? 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. 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. So, like, you're saying I should let my brother-in-law make any adjustments? 220 would be cool. 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 Niccol wrote "It used to be that the USA was pretty good at producing stuff teenaged boys could lose a finger or two playing with." |
#13
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If you are in USA or Canada wire 120/208 three phase. If you need 440 , 480.
277 , 575 , 347 ?600 use step transformers. All your lighting and most of your motors will work off of this system. Your utility company will have you install a seven jaw 3 1/2 element meter to measure your single phase and three phase loads. Try to keep away from demand metering, the penalties can really sour a fun day in the shop if your instantaneous demands are high and prolonged.Power factor is not something you want to have to monitor and correct. My two cents worth! Pete "Jess" wrote in message ... 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 |
#14
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"Jess" wrote in message ... 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. I have three phase, and have had it as long as I've had a shop (since '67). First shop was an open delta system, which is fine for light duty----no large motors, say, under 7-1/2 hp.. I now have a 400 amp service, again, delta. I had the option of 480, but didn't want to deal with the higher voltage, even though one of my machines (a cylindrical universal grinder) requires 480 volts. I have a transformer for that one machine. The one negative is that with a delta service, you have a wild leg (208 volts, the B phase) that can't be used for 120V service. That's no big deal, but it costs you one space out of three on your panel. You can use the space for 240 volts single phase, however, so something like a welder or water heater can occupy the otherwise unused space. If you select a delta service (240 volts), be sure to keep that in mind so you size your panel properly. The advantage of delta over wye (star) is the 240 volts instead of 208. Motors will run cooler--although you're not supposed to be sacrificing any power with the wye system. Dunno, I'm not an EE, nor an electrician. I do know that a close friend had problems with some CNC grinders when he moved to his new shop, equipped with 208 volts instead of 240. Hope this helps more than it confuses. Harold |
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Jess wrote:
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 I'm going to agree with the folks recommending against the 480v. That's the evil power, everyone I've ever discussed it with agrees. Another angle is that you need top quality stuff for 480, you just don't want to use used wire and plugs on it, where with 240 you can use stuff that's less than absolutely perfect. A little carbon tracking in a plug, it'll arc with 480v where it just doesn't seem to with 240. If you're willing to buy all new stuff, there's the natural gain of lower amperage draw with 480.. but it'll find any problems in your wiring, etc. far quicker than 240v. Motor insulation is no problem, the windings only see 240v either way, it's the plugs and wiring that's the issue. John |
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On Mon, 12 Sep 2005 15:51:38 -0500, Jess
wrote: Hi all, I would like some help / advice in outfitting my shop. My question is, which voltage should I specify - and why? Update: Thanks for all the help so far. OK, the 440v is out. Any future 400+v requirements will be avoided or met with my own transformer and new top notch gear downstream. Delta vs Wye?, 208 vs 240 ? It seems like there are some definite compromises there. In particular - whether or not you have 110v single and 240v single available, and whether you have three well balanced legs? (if I understand correctly). Any other additions to the delta / wye 208 /240 debate would be greatly appreciated. Thanks again for all the help. Jess |
#17
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Jess wrote:
On Mon, 12 Sep 2005 15:51:38 -0500, Jess wrote: Hi all, I would like some help / advice in outfitting my shop. My question is, which voltage should I specify - and why? Update: Thanks for all the help so far. OK, the 440v is out. Any future 400+v requirements will be avoided or met with my own transformer and new top notch gear downstream. Delta vs Wye?, 208 vs 240 ? It seems like there are some definite compromises there. In particular - whether or not you have 110v single and 240v single available, and whether you have three well balanced legs? (if I understand correctly). Any other additions to the delta / wye 208 /240 debate would be greatly appreciated. Thanks again for all the help. Jess Here's my opinion, for what it's worth, applied to a non-commercial shop in the U.S. The problem with 480V is not so much a safety issue (and the real danger is the available fault current more than the voltage) as one of economics. 480 volt wiring methods are the same as with lower voltages, but the power panels and breakers tend to be more costly and you'll need to provide for 120/240 single phase loads with a separate panel and transformer on a branch circuit. Unless you have several motors in the greater than 10 to 15 hp range rule 480V services out from the start. 120/208 wye service is not really appropriate for a shop either, this service is good for lighting but not so good for motor loads, save it for the next strip mall or office building you build. It's 208 because that's what your stuck with when you set out to get 120 volts phase to neutral in a wye connection. For a hobby or small commercial shop go with a 240v center tapped delta service. You get 240 three phase and 240/120 single phase all out of one panel. Yes, you'll end up with a few unused slots in the panel due to the 'high leg', but who cares. If it's a mystery as to which phases supply which voltages to neutral don't even take the panel cover screws out and leave it to someone who knows, but it's really no big deal. The power company, at least around here, prefers this service as it generally has a lower installed cost, they can get by with just two transformers and wire it open delta. To you, the end user, it generally won't matter. You'll have extra work to due for single voltage 480V motors, but most machine tool motors are of the dual voltage variety anyway. I'm hard pressed for a valid reason to even consider another service for a small shop. Regards Paul -- ----------------------------------------- It's a Linux world....well, it oughta be. ----------------------------------------- |
#18
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120/208 wye service is not really appropriate for a shop either, this
My father was an electrician and I use to help him when I was a kid. At that time I thought 208 was the best because you could easily get 120 for lights and run real motors on three phase. Now I am not very fond of 208. You should check your machines to see if the motors will actually run on 208. I suspect that many (or most) of than will not. In my home shop I run all my 3 phase motors with VFDs. I hate 208 volt motors because they do not work well with a VFD and tend to over heat because they are getting 240V instead of 208V. I have experimented with VFD parameters and managed to program a Teco drive to put out 208 instead of 240. My 1/2HP surface grinder works ok this way, but the 1HP motor on my rockwell lathe didn't like it much so I had to buy a new motor. chuck |
#19
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Paul Batozech wrote:
Jess wrote: On Mon, 12 Sep 2005 15:51:38 -0500, Jess wrote: Hi all, I would like some help / advice in outfitting my shop. My question is, which voltage should I specify - and why? Update: Thanks for all the help so far. OK, the 440v is out. Any future 400+v requirements will be avoided or met with my own transformer and new top notch gear downstream. Delta vs Wye?, 208 vs 240 ? It seems like there are some definite compromises there. In particular - whether or not you have 110v single and 240v single available, and whether you have three well balanced legs? (if I understand correctly). Any other additions to the delta / wye 208 /240 debate would be greatly appreciated. Thanks again for all the help. Jess Here's my opinion, for what it's worth, applied to a non-commercial shop in the U.S. The problem with 480V is not so much a safety issue (and the real danger is the available fault current more than the voltage) as one of economics. 480 volt wiring methods are the same as with lower voltages, but the power panels and breakers tend to be more costly and you'll need to provide for 120/240 single phase loads with a separate panel and transformer on a branch circuit. Unless you have several motors in the greater than 10 to 15 hp range rule 480V services out from the start. I have a 480 volt service to my shop and house. The main down side like mentioned above is the transformer to supply the lower voltage power. The problem with the transformer is it's cost of operation!! They suck lots of power just sitting there running! Having said that though, I would still run the same system for my shop if I was going to reinstall it today. William... |
#20
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"William" wrote in message ... snip----- I have a 480 volt service to my shop and house. The main down side like mentioned above is the transformer to supply the lower voltage power. The problem with the transformer is it's cost of operation!! They suck lots of power just sitting there running! Having said that though, I would still run the same system for my shop if I was going to reinstall it today. William... I've given the idling transformer some thought, but I'm in the opposite position. I have only one machine that will run on 480 volts (can't be run lower), so my 3 phase delta 240 volt system is perfect for my application. The 480 volt transformer for the one machine will be kept turned off unless the machine is in service. That way I'm not heating the shop unnecessarily. I avoided the lost spaces in my 3 phase panel by installing a single phase and a three phase panel. the shop is large, so it justified both panels. Only the 3 phase is on a demand meter, so I minimize my chances of paying high prices for power. On the other hand, I do have two power bills, but that was inevitable if I wanted three phase service. Policy at our Public Utility District is that 3 phase service is considered industrial------not residential-----so you have to have different metering. 3 phase is always on a demand meter here. No way was I going to install a wye system. Harold |
#21
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On Thu, 15 Sep 2005 12:04:56 -0700, Harold and Susan Vordos wrote:
3 phase is always on a demand meter here. I've seen the term "demand metering" mentioned here several times and have gleaned that it can be expensive for some reason. What is demand metering and why is it more expensive than other types of metering? (My dream is to sell my house when I retire and live in a shop which will have 3 phase power from the util. co.) |
#22
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Harold and Susan Vordos wrote:
"William" wrote in message ... snip----- I have a 480 volt service to my shop and house. The main down side like mentioned above is the transformer to supply the lower voltage power. The problem with the transformer is it's cost of operation!! They suck lots of power just sitting there running! Having said that though, I would still run the same system for my shop if I was going to reinstall it today. William... I've given the idling transformer some thought, but I'm in the opposite position. I have only one machine that will run on 480 volts (can't be run lower), so my 3 phase delta 240 volt system is perfect for my application. The 480 volt transformer for the one machine will be kept turned off unless the machine is in service. That way I'm not heating the shop unnecessarily. The idle current form a small transformer that you run one machine off will not be that bad . My problem is that I needed/wanted to have 200 amps of power on the lower voltage (120/208) in my case derived from my single 600 amp 480/277 feed. since it's on my side of the meter it's covered by the NEC and that requires a 75kva transformer for the 200 amps even though I will NEVER pull 200 amps through it! In fact the Utility co feeds the whole 600 amp service with 3, 25kva cans on the pole ( at my request they will replace them with larger ones if I want/need them but they charge a min fee based on the size of the cans so the smaller ones work for me!) I avoided the lost spaces in my 3 phase panel by installing a single phase and a three phase panel. the shop is large, so it justified both panels. Only the 3 phase is on a demand meter, so I minimize my chances of paying high prices for power. On the other hand, I do have two power bills, but that was inevitable if I wanted three phase service. Policy at our Public Utility District is that 3 phase service is considered industrial------not residential-----so you have to have different metering. 3 phase is always on a demand meter here. My system is all demand metered ( and only one bill that way) BUT, at the magic "75kva average over a 15 min interval " they kick in the demand charge ( if during the 3 summer / 3 winter peak months) You can BET I will never let that happen as it's CHA CHING!! if it does. At almost $15.00 per KVA + the KW charge for the whole month. The 75 kva is a lot of power though and I don't think I will exceed that. No way was I going to install a wye system. I wanted the wye and the 277 volts for the HID lighting is great. The cost of Cu wire is out of sight and I can run most of my machines off 12 gauge wire if I want. I only have 2 machines that didn't like the 480 volts, and one runs fine on the 208 and the other (the blade welder for the band saw) would have probably worked ok but I picked up a single phase 480volt to 240 volt transformer for cheep for the times I have to use that unit. William.... |
#23
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On Mon, 12 Sep 2005 15:51:38 -0500, Jess
wrote: 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? If you have any 480V loads to run and you can get a 480V 3Ph feed from the utility without a hassle or a huge price penalty compared to 240V 3Ph, it's always far simpler to drop a 480V feed down to 240V for most of your loads with a cheap used transformer than it is to boost a 240V feed up to 480V. And a 200A @ 480V feed goes a whole lot further. But as has been pointed out, 480V demands some serious respect because it will reach out and bite you hard, and things tend to "blow up reel gud" ;-) with very little provocation. You put in the 480V meter section and main, a small (12 or 18 position) 480V distribution breaker panel to feed any machines that must be run at 480V, or fused safety switches - and be sure to run it in as 4-wire with a neutral in case you ever need 277V for lights. Then you install your 480V-240V transformer, and a larger (and much cheaper) 240V 3Ph panel for the bulk of your equipment. If you want to run 277V lighting in a large shop, pay a bit more for the light fixtures with individual fuses inside. Without them, one ballast in a long string of lights goes bad and grounds out, and you go nuts opening every single stupid fixture to find the culprit. Or you split the circuit and test, and hope the circuit breaker lives through the repeated short-circuit torture test. BT, DT... I do have some small bench top and hand held machines that require 110v single phase. Run a separate "lights and plugs" feed out to the shop building from your house's 120-240V 1Ph panel feed, or leave the existing one hooked up. This way, you can kill all the shop power at the 3Ph Main to work on it, or just to kill the parasitic loads from the transformers and keep "unauthorized personnel" from messing with your toys, and not be in the dark. With that power coming in on a totally separate feeder you keep the motor start surges and welder spikes away from the more sensitive gear. And no lights dimming when you hit the big switches. Also, see mentions of demand metering and higher rates for 'commercial power' mentioned elsewhere - that way the lights, furnace blower, computers, clocks, and other incidental loads that tend to add up fast are being metered at the residential rate. 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. Consider getting three buck-boost transformers to drop a 240V or 208V line to 200V, depending on the price it's probably cheaper than a new motor. And you can use some ridiculously small and cheap transformers for that, even when buying new. 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. A lot of equipment does both 208V and 240V, the current is slightly higher at 208V. Makes it easier to wire up small industrial parks at 208V without people constantly making "Oopsies" hooking up 120V stuff to the ~190V 'High Leg' of a 120/240V Delta service. If I had my way, ALL houses would be able to get either 120/208V Wye or 120/240V Delta feeds on demand - Just putting the largest motor loads like air conditioning/heat pump compressors on 3-phase increases the energy efficiency enough to make for a short payback period. "But that will never happen - It would simply make too much sense." (© BLB) -- Bruce -- -- Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop Electrician for Westend Electric - CA726700 5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545 Spamtrapped address: Remove the python and the invalid, and use a net. |
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Which 3 phase Voltage to get?
Hi Jess
One other thing you might want to consider, is if your shop is already wired for 120/240 single phase the insulation on the present wire is probably not rated for 480 service. 480 service requires wire with 600 volt insulation. This would not be a consideration with 240 three service. Travis "Jess" wrote in message ... 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 |
#25
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Which 3 phase Voltage to get?
For a hobby or small commercial shop go with a 240v center tapped delta
service. You get 240 three phase and 240/120 single phase all out of one panel. Yes, you'll end up with a few unused slots in the panel due to the 'high leg', but who cares. If it's a mystery as to which phases supply which voltages to neutral don't even take the panel cover screws out and leave it to someone who knows, but it's really no big deal. The power company, at least around here, prefers this service as it generally has a lower installed cost, they can get by with just two transformers and wire it open delta. To you, the end user, it generally won't matter. You'll have extra work to due for single voltage 480V motors, but most machine tool motors are of the dual voltage variety anyway. I'm hard pressed for a valid reason to even consider another service for a small shop. You dont' mention if this is an additional service or a replacement service. I had three phase installed a few years ago. It was a replacement service. I went with 240V center tapped delta. It's the way to go in my opionion. It will maintain all of your single phase service with no(minimal) changes. You will gain "true" three phase. Yes, there is a wild leg that needs to be kept in mind when considering single phase loads. It's not really a big deal. Check with your power provider. They will have a PE on staff that can answer any questions. They can tell you what they will do, and what expense it may be to you. Going to 240V 3ph cost me nothing for installation. 208 or 480 would have been a minimal fee, but would have required other "local" infrastructure changes to accomodate. As many have suggested, stay away from 480V power. It steps things up to a realm where you NEED to know exactly what you are doing or you will hurt/kill yourself/others. It will also increase the expense of equipment/materials. Everything will need to be 600V rated. JW |
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