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#1
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3 phase service
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl |
#2
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3 phase service
On Oct 25, 12:58*pm, Karl Townsend
wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl I have seen this done by using a Delta transformer with a center tap that is grounded. Each hot side of grounded winding is 120 VAC and 220 VAC between them. This can lead to all sorts of issues when hooking up 3 phase with internal 110 taps. the 3 phase is no longer ballanced around ground. Lets just say some circute breakers got a work out untill I figured it out. |
#3
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3 phase service
On Mon, 25 Oct 2010 14:58:56 -0500, Karl Townsend
wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl Unless you have equipment with conflicting requirements, I'd plan for a 208 wye service in the shop in order to get get both three phase and 120 single phase. Regardless of what you do in the future, it sounds like you have enough wire buried to feed the house from the shop. -- Ned Simmons |
#4
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3 phase service
On 2010-10-25, Ned Simmons wrote:
On Mon, 25 Oct 2010 14:58:56 -0500, Karl Townsend wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl Unless you have equipment with conflicting requirements, I'd plan for a 208 wye service in the shop in order to get get both three phase and 120 single phase. Regardless of what you do in the future, it sounds like you have enough wire buried to feed the house from the shop. And how is he going to have 220 in the house? i |
#5
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3 phase service
On Mon, 25 Oct 2010 15:39:24 -0500, Ignoramus3392
wrote: On 2010-10-25, Ned Simmons wrote: On Mon, 25 Oct 2010 14:58:56 -0500, Karl Townsend wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl Unless you have equipment with conflicting requirements, I'd plan for a 208 wye service in the shop in order to get get both three phase and 120 single phase. Regardless of what you do in the future, it sounds like you have enough wire buried to feed the house from the shop. And how is he going to have 220 in the house? i He'll have 208/120, like most apartment buildings. -- Ned Simmons |
#6
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3 phase service
On 2010-10-25, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. That would be "208 volts". So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. I would just have separate transformers if it was up to me. i |
#7
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3 phase service
On Mon, 25 Oct 2010 15:39:00 -0500, Ignoramus3392
wrote: On 2010-10-25, Karl Townsend wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. That would be "208 volts". So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. I would just have separate transformers if it was up to me. i Then you're paying for the xformer losses. With a 208/120 wye service the power company keeps the transformers warm on their dime. -- Ned Simmons |
#8
Posted to rec.crafts.metalworking
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3 phase service
Karl Townsend wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl Two legs and neutral of 120/208V Wye three phase service is generally considered to be equivalent to 120/240V single phase service for most uses. 120V only appliances will see no difference at all, 240V appliances will be minimally affected and many have dual 208/240V ratings anyway these days since apartments often have 120/208V service. The key thing to watch out for with three phase service is the rates such as the common peak metered commercial rates where you end up paying for your highest use day, not your actual use. The four wires are correct since either way, one end is the service end with ground and neutral bonded and the other is a sub. |
#9
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3 phase service
On Mon, 25 Oct 2010 16:03:09 -0500, "Pete C."
wrote: Karl Townsend wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl Two legs and neutral of 120/208V Wye three phase service is generally considered to be equivalent to 120/240V single phase service for most uses. 120V only appliances will see no difference at all, 240V appliances will be minimally affected and many have dual 208/240V ratings anyway these days since apartments often have 120/208V service. The key thing to watch out for with three phase service is the rates such as the common peak metered commercial rates where you end up paying for your highest use day, not your actual use. The four wires are correct since either way, one end is the service end with ground and neutral bonded and the other is a sub. Thanks Pete and Ned. This is a big enough job we don't want to do it twice. Karl |
#10
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3 phase service
On 10/25/2010 02:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. There are essentially 4 ways to wire a 3-phase 2xx Volt service. There is 240 V delta, and 208 V Wye service. 240 V delta is not what you want here. 208 Wye service will work, but if you hook the house to 2 of the 3-phase hots, you get 208 V on the appliances that expect 240. Check the air conditioners, etc. carefully for their ability to run off 208. Then, there are two variants of the above systems, you may not be able to get these installed by your local electric company. One is corner-grounded delta, that gives you 2 240 V hots, good for running machine tool motors, the advantage is you can use normal 2-pole electrical panels and 2-pule breakers. No 120 V in that service, so not suitable for the house. The last form is center-grounded delta. It gives you both a 3-phase service, as well as one phase that is grounded at the center-tap. So, those two hots and neutral look exactly like single-phase home service. There is a third leg to provide the 3rd phase. IF!! you can get your electric utility to provide this service, it probably is the best choice, as you get real 240 V single phase service PLUS 3-phase with only 5 wires (3 phases, neutral and ground). Jon |
#11
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3 phase service
Jon Elson wrote: On 10/25/2010 02:58 PM, Karl Townsend wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. There are essentially 4 ways to wire a 3-phase 2xx Volt service. There is 240 V delta, and 208 V Wye service. 240 V delta is not what you want here. 208 Wye service will work, but if you hook the house to 2 of the 3-phase hots, you get 208 V on the appliances that expect 240. Check the air conditioners, etc. carefully for their ability to run off 208. Then, there are two variants of the above systems, you may not be able to get these installed by your local electric company. One is corner-grounded delta, that gives you 2 240 V hots, good for running machine tool motors, the advantage is you can use normal 2-pole electrical panels and 2-pule breakers. No 120 V in that service, so not suitable for the house. The last form is center-grounded delta. It gives you both a 3-phase service, as well as one phase that is grounded at the center-tap. So, those two hots and neutral look exactly like single-phase home service. There is a third leg to provide the 3rd phase. IF!! you can get your electric utility to provide this service, it probably is the best choice, as you get real 240 V single phase service PLUS 3-phase with only 5 wires (3 phases, neutral and ground). Jon That last one is also known as "wild leg" delta service since the third phase is not at 120V relative to the ground/neutral, and that third phase is normally color coded orange to identify it. It wouldn't be a problem for the house, since that wild leg wouldn't be fed to the house, but it has been known to cause confusion and blown up 120V stuff in many installations. Another issue with this type of service is that some three phase machines may want 120/208V Wye service with it's neutral to phase voltage at 120V for all phases. Generally, if you ask the utility for three phase service, you will be getting 120/208V Wye service unless you specifically ask for something different. Expect a lot of questions if you ask for three phase service and a lot more if you ask for anything but the common commercial 120/208V Wye service. As noted, most appliances these days are 208/240V rated since 120/208V service is very common in apartment buildings. Check everything to be sure, but you're not likely to find much that isn't ok with 208V. |
#12
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3 phase service
Pete C. wrote:
Jon Elson wrote: On 10/25/2010 02:58 PM, Karl Townsend wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. There are essentially 4 ways to wire a 3-phase 2xx Volt service. There is 240 V delta, and 208 V Wye service. 240 V delta is not what you want here. 208 Wye service will work, but if you hook the house to 2 of the 3-phase hots, you get 208 V on the appliances that expect 240. Check the air conditioners, etc. carefully for their ability to run off 208. Then, there are two variants of the above systems, you may not be able to get these installed by your local electric company. One is corner-grounded delta, that gives you 2 240 V hots, good for running machine tool motors, the advantage is you can use normal 2-pole electrical panels and 2-pule breakers. No 120 V in that service, so not suitable for the house. The last form is center-grounded delta. It gives you both a 3-phase service, as well as one phase that is grounded at the center-tap. So, those two hots and neutral look exactly like single-phase home service. There is a third leg to provide the 3rd phase. IF!! you can get your electric utility to provide this service, it probably is the best choice, as you get real 240 V single phase service PLUS 3-phase with only 5 wires (3 phases, neutral and ground). Jon That last one is also known as "wild leg" delta service since the third phase is not at 120V relative to the ground/neutral, and that third phase is normally color coded orange to identify it. It wouldn't be a problem for the house, since that wild leg wouldn't be fed to the house, but it has been known to cause confusion and blown up 120V stuff in many installations. Another issue with this type of service is that some three phase machines may want 120/208V Wye service with it's neutral to phase voltage at 120V for all phases. Generally, if you ask the utility for three phase service, you will be getting 120/208V Wye service unless you specifically ask for something different. Expect a lot of questions if you ask for three phase service and a lot more if you ask for anything but the common commercial 120/208V Wye service. As noted, most appliances these days are 208/240V rated since 120/208V service is very common in apartment buildings. Check everything to be sure, but you're not likely to find much that isn't ok with 208V. The 240 volt systems were designed to save the power company from installing an extra pole transformer for 240 volt single phase service. With 208 single phase two pole transformers were needed, and if three phase were required you needed to install three transformers to obtain the star or wye configuration. By using the center-tapped transformer neutral transformer it eliminated a second transformer. If three phase was required it was necessary to add only one more transformer rather than two, except when higher power rating were required and a third transformer is used. That was the difference between open leg delta and a full delta secondary. A lot of people are confused by seeing only two high voltage primary wires and getting fed with three phase into their building but that is very common. John |
#13
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3 phase service
On Mon, 25 Oct 2010 23:28:06 -0400, John
wrote: Pete C. wrote: Jon Elson wrote: On 10/25/2010 02:58 PM, Karl Townsend wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. There are essentially 4 ways to wire a 3-phase 2xx Volt service. There is 240 V delta, and 208 V Wye service. 240 V delta is not what you want here. 208 Wye service will work, but if you hook the house to 2 of the 3-phase hots, you get 208 V on the appliances that expect 240. Check the air conditioners, etc. carefully for their ability to run off 208. Then, there are two variants of the above systems, you may not be able to get these installed by your local electric company. One is corner-grounded delta, that gives you 2 240 V hots, good for running machine tool motors, the advantage is you can use normal 2-pole electrical panels and 2-pule breakers. No 120 V in that service, so not suitable for the house. The last form is center-grounded delta. It gives you both a 3-phase service, as well as one phase that is grounded at the center-tap. So, those two hots and neutral look exactly like single-phase home service. There is a third leg to provide the 3rd phase. IF!! you can get your electric utility to provide this service, it probably is the best choice, as you get real 240 V single phase service PLUS 3-phase with only 5 wires (3 phases, neutral and ground). Jon That last one is also known as "wild leg" delta service since the third phase is not at 120V relative to the ground/neutral, and that third phase is normally color coded orange to identify it. It wouldn't be a problem for the house, since that wild leg wouldn't be fed to the house, but it has been known to cause confusion and blown up 120V stuff in many installations. Another issue with this type of service is that some three phase machines may want 120/208V Wye service with it's neutral to phase voltage at 120V for all phases. Generally, if you ask the utility for three phase service, you will be getting 120/208V Wye service unless you specifically ask for something different. Expect a lot of questions if you ask for three phase service and a lot more if you ask for anything but the common commercial 120/208V Wye service. As noted, most appliances these days are 208/240V rated since 120/208V service is very common in apartment buildings. Check everything to be sure, but you're not likely to find much that isn't ok with 208V. The 240 volt systems were designed to save the power company from installing an extra pole transformer for 240 volt single phase service. With 208 single phase two pole transformers were needed, and if three phase were required you needed to install three transformers to obtain the star or wye configuration. By using the center-tapped transformer neutral transformer it eliminated a second transformer. If three phase was required it was necessary to add only one more transformer rather than two, except when higher power rating were required and a third transformer is used. That was the difference between open leg delta and a full delta secondary. A lot of people are confused by seeing only two high voltage primary wires and getting fed with three phase into their building but that is very common. John Guys, thanks for the discussion on types of three phase. Bit more to this than I thought. he's talked with the power company and will get FAR lower install cost if he provides and maintains the transformer. We're, of course, looking for a used one. With all the different primary voltages out there and now all the flavors of three phase, this looks like a tuff task. Karl |
#14
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3 phase service
Karl Townsend wrote:
On Mon, 25 Oct 2010 23:28:06 -0400, wrote: Pete C. wrote: Jon Elson wrote: On 10/25/2010 02:58 PM, Karl Townsend wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. There are essentially 4 ways to wire a 3-phase 2xx Volt service. There is 240 V delta, and 208 V Wye service. 240 V delta is not what you want here. 208 Wye service will work, but if you hook the house to 2 of the 3-phase hots, you get 208 V on the appliances that expect 240. Check the air conditioners, etc. carefully for their ability to run off 208. Then, there are two variants of the above systems, you may not be able to get these installed by your local electric company. One is corner-grounded delta, that gives you 2 240 V hots, good for running machine tool motors, the advantage is you can use normal 2-pole electrical panels and 2-pule breakers. No 120 V in that service, so not suitable for the house. The last form is center-grounded delta. It gives you both a 3-phase service, as well as one phase that is grounded at the center-tap. So, those two hots and neutral look exactly like single-phase home service. There is a third leg to provide the 3rd phase. IF!! you can get your electric utility to provide this service, it probably is the best choice, as you get real 240 V single phase service PLUS 3-phase with only 5 wires (3 phases, neutral and ground). Jon That last one is also known as "wild leg" delta service since the third phase is not at 120V relative to the ground/neutral, and that third phase is normally color coded orange to identify it. It wouldn't be a problem for the house, since that wild leg wouldn't be fed to the house, but it has been known to cause confusion and blown up 120V stuff in many installations. Another issue with this type of service is that some three phase machines may want 120/208V Wye service with it's neutral to phase voltage at 120V for all phases. Generally, if you ask the utility for three phase service, you will be getting 120/208V Wye service unless you specifically ask for something different. Expect a lot of questions if you ask for three phase service and a lot more if you ask for anything but the common commercial 120/208V Wye service. As noted, most appliances these days are 208/240V rated since 120/208V service is very common in apartment buildings. Check everything to be sure, but you're not likely to find much that isn't ok with 208V. The 240 volt systems were designed to save the power company from installing an extra pole transformer for 240 volt single phase service. With 208 single phase two pole transformers were needed, and if three phase were required you needed to install three transformers to obtain the star or wye configuration. By using the center-tapped transformer neutral transformer it eliminated a second transformer. If three phase was required it was necessary to add only one more transformer rather than two, except when higher power rating were required and a third transformer is used. That was the difference between open leg delta and a full delta secondary. A lot of people are confused by seeing only two high voltage primary wires and getting fed with three phase into their building but that is very common. John Guys, thanks for the discussion on types of three phase. Bit more to this than I thought. he's talked with the power company and will get FAR lower install cost if he provides and maintains the transformer. We're, of course, looking for a used one. With all the different primary voltages out there and now all the flavors of three phase, this looks like a tuff task. Karl Karl, Search for pole transformers. If its only the installation cost that is different I would go for the extra buck and let the power company own the transformer. If you happen to have one blow from lightning or some other problem it will be a lot faster if they come and replace it rather than you searching for a replacement. Also wait till you check on some of the prices of those pole pigs. Unless you are going to draw a lot of power you can run open delta with one 240 center tapped grounded and one 240 single phase unit. You only need two legs of the delta to get the three phase but you get a little less regulation and can only pull the wattage of the two transformers. Most smaller shops on three phase only get two pigs on the pole. John |
#15
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3 phase service
John wrote:
With 208 single phase two pole transformers were needed, and if three phase were required you needed to install three transformers to obtain the star or wye configuration. By using the center-tapped transformer neutral transformer it eliminated a second transformer. If three phase was required it was necessary to add only one more transformer rather than two, except when higher power rating were required and a third transformer is used. That was the difference between open leg delta and a full delta secondary. A lot of people are confused by seeing only two high voltage primary wires and getting fed with three phase into their building but that is very common. Do you mean 2 high voltage wires or 2 transformers? Three phase is possible with 2 transformers, but not with 2 high voltage lines. |
#16
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3 phase service
On Oct 26, 12:27*pm, Jim Stewart wrote:
John wrote: With 208 single phase two pole transformers were needed, and if three phase were required you needed to install three transformers to obtain the star or wye configuration. By using the center-tapped transformer neutral transformer it eliminated a second transformer. If three phase was required it was necessary to add only one more transformer rather than two, except when higher power rating were required and a third transformer is used. That was the difference between open leg delta and a full delta secondary. A lot of people are confused by seeing only two high voltage primary wires and getting fed with three phase into their building but that is very common. Do you mean 2 high voltage wires or 2 transformers? Three phase is possible with 2 transformers, but not with 2 high voltage lines. Open Delta. Only two transformers, and ONLY two high voltage lines to feed the TWO transformers. Pretty common all over. |
#17
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3 phase service
Jim Stewart wrote:
John wrote: With 208 single phase two pole transformers were needed, and if three phase were required you needed to install three transformers to obtain the star or wye configuration. By using the center-tapped transformer neutral transformer it eliminated a second transformer. If three phase was required it was necessary to add only one more transformer rather than two, except when higher power rating were required and a third transformer is used. That was the difference between open leg delta and a full delta secondary. A lot of people are confused by seeing only two high voltage primary wires and getting fed with three phase into their building but that is very common. Do you mean 2 high voltage wires or 2 transformers? Three phase is possible with 2 transformers, but not with 2 high voltage lines. Three phase can be had off of two hi voltage primary wires. It is just that you have no choice but to go open delta on the lv. John |
#18
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3 phase service
"Karl Townsend" wrote in message ... "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl Suggest the "center tapped grounded delta" system... SEE: http://www.iatse611.org/education/Electrics.htm --just don't forget....use phase "B" ONLY for 3 phase loads because it has a 208 volt potential to ground /neutral. -- |
#19
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3 phase service
I"d leave the house as it is and pull out the long runs for use in
the shop once done. I have single phase myself and added three phase rotary. I could have the power line deliver me 3 phase - as I have 1500 feet 42KV 2 phase and the house and shop tap off only one of the two legs. I'm a side branch from the state highway - delivering power to my site - once a sawmill. Mill is long gone, but the power allows all sort of possible future expansions or changes. Martin On 10/25/2010 2:58 PM, Karl Townsend wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl |
#20
Posted to rec.crafts.metalworking
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3 phase service
On Oct 25, 12:58*pm, Karl Townsend
wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl One consideration that is not electrically oriented is if there is a house fire and there is no meter for the firefighters to pull for their safety, they will just stand by and watch the house burn. Paul |
#21
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3 phase service
Meter on the pole or in the pad transformer - normally on the end
and the sides hinge open. Nothing is hardwired by professionals. Our big pad units had meters on then. Martin On 10/26/2010 1:16 PM, KD7HB wrote: On Oct 25, 12:58 pm, Karl wrote: "The Kid" is putting in underground wiring to his outbuildings. For now, power will come from the house to the shop. The shop sits twenty feet from a three phase line. future plans is to install a three phase service to the shop, cut the ordinal transformer out, and then feed one phase back to the house from the wiring being installed now. OK, a one phase house service has two 110 legs on the same phase opposite polarity to get 220 across the two hot wires, neutral is the center tap. As I understand it you in effect get three 110 hot wires 120 degrees apart in the phasing for three phase with the center tap for neutral. So, can you run single phase 220 off this? Need any special provisions installed now? He's putting in conduit - four wires - two hot, neutral and ground. Karl One consideration that is not electrically oriented is if there is a house fire and there is no meter for the firefighters to pull for their safety, they will just stand by and watch the house burn. Paul |
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