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#1
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440 volt three phase question
I've had the moment to work on 440 volt roof top heating and AC.
Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) -- Christopher A. Young Learn more about Jesus www.lds.org .. |
#2
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440 volt three phase question
"Stormin Mormon" wrote in message ... I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) -- Christopher A. Young Learn more about Jesus www.lds.org . No, it's 220 more or less, to ground |
#3
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440 volt three phase question
On May 27, 10:03*am, "Stormin Mormon"
wrote: I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? No. (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) |
#4
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440 volt three phase question
Stormin Mormon wrote:
I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) There is normally a transformer in the panel to give you 120 volts if 120 volts is needed there. Don't you have a meter? -- LSMFT I haven't spoken to my wife in 18 months. I don't like to interrupt her. |
#5
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440 volt three phase question
On May 27, 4:03�pm, "Stormin Mormon"
wrote: I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) -- Christopher A. Young Learn more about Jesus �www.lds.org . With any three phase sytem (assuming it's symetrical) the line volts = phase volts divided by root three ie in your case 440/1.73 =254 This is because the phases are 120 degrees apart. This is the voltage that would appear between phase and ground or phase and neutral. However it's not a good idea to run electrical equipment between phase and ground as there is a good chance of electrocuting yourself or someone else. The someone else could be some distance away too. |
#6
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440 volt three phase question
On May 27, 11:03*am, "Stormin Mormon"
wrote: I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) -- Christopher A. Young Learn more about Jesus *www.lds.org . How old is this roof top unit... Seriously 440 volts ? Are you sure that it isn't 480 volts ? I asked the _age_ of the unit because there is supposed to be a service outlet for 120 volt powered tools for maintaining the roof top equipment installed somewhere near the unit... And no, with a 3 phase 480 volt system it is typically 277 volts on each leg... ~~ Evan |
#7
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440 volt three phase question
Thank you. Saves me building a device, and not have it work.
-- Christopher A. Young Learn more about Jesus www.lds.org .. wrote in message ... The nominal 480 wye to neutral is 277 volts. That is why you see 277v lighting in big buildings |
#8
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440 volt three phase question
Oh, thank you. I didn't know.
-- Christopher A. Young Learn more about Jesus www.lds.org .. "keith" wrote in message ... On May 27, 10:03 am, "Stormin Mormon" wrote: I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? No. |
#9
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440 volt three phase question
Oh, thank you. I didn't know.
-- Christopher A. Young Learn more about Jesus www.lds.org .. "RBM" wrote in message ... No, it's 220 more or less, to ground |
#10
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440 volt three phase question
Where I was working, there was a GFCI convenience outlet on the side
(120 VAC) but that got me to thinking. And, I'm learning. -- Christopher A. Young Learn more about Jesus www.lds.org .. "LSMFT" wrote in message ... There is normally a transformer in the panel to give you 120 volts if 120 volts is needed there. Don't you have a meter? -- LSMFT I haven't spoken to my wife in 18 months. I don't like to interrupt her. |
#11
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440 volt three phase question
Thanks. That sounds reasonable. I do try not to use grounds as
neutrals, if at all possible. -- Christopher A. Young Learn more about Jesus www.lds.org .. "harry" wrote in message ... With any three phase sytem (assuming it's symetrical) the line volts = phase volts divided by root three ie in your case 440/1.73 =254 This is because the phases are 120 degrees apart. This is the voltage that would appear between phase and ground or phase and neutral. However it's not a good idea to run electrical equipment between phase and ground as there is a good chance of electrocuting yourself or someone else. The someone else could be some distance away too. |
#12
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440 volt three phase question
How old is this roof top unit... Seriously 440 volts ? Are you sure that it isn't 480 volts ? CY: The unit looks maybe ten years old. It may well been 480, and I typed it wong. I asked the _age_ of the unit because there is supposed to be a service outlet for 120 volt powered tools for maintaining the roof top equipment installed somewhere near the unit... CY: Actually, this one did have a convenience outlet. But,t hat gets me thinking. And no, with a 3 phase 480 volt system it is typically 277 volts on each leg... CY: Thanks. ~~ Evan |
#13
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440 volt three phase question
On 5/27/2010 1:03 PM Evan spake thus:
On May 27, 11:03 am, "Stormin Mormon" wrote: I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) How old is this roof top unit... Seriously 440 volts ? Are you sure that it isn't 480 volts ? Right; we should all tighten up our terminology, nominal voltage-wise. It's 120, 240 and 480. *Not* 110, 220 and 440. (Not to mention all those weird older numbers that were used, like 117 volts: WTF did that come from???) -- The fashion in killing has an insouciant, flirty style this spring, with the flaunting of well-defined muscle, wrapped in flags. - Comment from an article on Antiwar.com (http://antiwar.com) |
#14
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440 volt three phase question
Evan wrote:
On May 27, 11:03 am, "Stormin Mormon" wrote: I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) -- Christopher A. Young Learn more about Jesus www.lds.org . How old is this roof top unit... Seriously 440 volts ? Are you sure that it isn't 480 volts ? I asked the _age_ of the unit because there is supposed to be a service outlet for 120 volt powered tools for maintaining the roof top equipment installed somewhere near the unit... And no, with a 3 phase 480 volt system it is typically 277 volts on each leg... ~~ Evan Usually, equipment is rated for a range of voltages. A lot of HVAC equipment has different taps on the 24 volt control transformer to pick a different primary voltage. I've seen some air handlers that had a tap on the control transformer for 110 volts and another for 120 volts. Of course on larger package units there will be taps on the primary of the control transformer to choose between 208 or 240. I've seen a lot of blower motors that show a rating of 100-125 VAC 60 Hz on the nameplate. TDD |
#15
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440 volt three phase question
" I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) How old is this roof top unit... Seriously 440 volts ? Are you sure that it isn't 480 volts ? Right; we should all tighten up our terminology, nominal voltage-wise. It's 120, 240 and 480. *Not* 110, 220 and 440. (Not to mention all those weird older numbers that were used, like 117 volts: WTF did that come from???) *I have found that the actual voltage varies by power company. One company in NJ supplies 460/265 volts while another supplies 480/277. It is quite possible that Stormin is dealing with 440 volts. When I worked for my father decades ago he did a lot of industrial work and we quite often had to add buck and boost transformers to equipment because the juice from the power company did not match the nameplate requirements for a machine. |
#16
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440 volt three phase question
John Grabowski wrote:
.... *I have found that the actual voltage varies by power company. One company in NJ supplies 460/265 volts while another supplies 480/277. ... More than likely it's owing to variations in distribution or even local voltage drops rather than a difference in system generation setpoints between utilities. -- |
#17
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440 volt three phase question
*I have found that the actual voltage varies by power company. One company in NJ supplies 460/265 volts while another supplies 480/277. ... More than likely it's owing to variations in distribution or even local voltage drops rather than a difference in system generation setpoints between utilities. *Many years ago I had an issue with the voltage at a hospital that I was working at. It seemed that there was low voltage everywhere. I had the power company come in and monitor the building for a week, but they assured me that they only supply 460/265 and that is what we were getting. The ballasts for the fluorescent lighting were rated for 277 volts. I had to go to every transformer in the building and change the taps so that we could get 120 volts out of an outlet instead of the 102-105. I also had to install a few buck and boost transformers on some A/C equipment. Of course variation in distribution, voltage drop and distance from transformers does have an effect. |
#18
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440 volt three phase question
On May 27, 5:22*pm, "Stormin Mormon"
wrote: Oh, thank you. I didn't know. -- Christopher A. Young Learn more about Jesus *www.lds.org . "RBM" wrote in message ... *No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne |
#19
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440 volt three phase question
On 5/28/2010 5:36 AM John Grabowski spake thus:
" I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) How old is this roof top unit... Seriously 440 volts ? Are you sure that it isn't 480 volts ? Right; we should all tighten up our terminology, nominal voltage-wise. It's 120, 240 and 480. *Not* 110, 220 and 440. (Not to mention all those weird older numbers that were used, like 117 volts: WTF did that come from???) *I have found that the actual voltage varies by power company. One company in NJ supplies 460/265 volts while another supplies 480/277. It is quite possible that Stormin is dealing with 440 volts. Don't doubt you at all; however, the *nominal* voltages are still 120/240/480. What you're describing are basically under-voltage situations. -- The fashion in killing has an insouciant, flirty style this spring, with the flaunting of well-defined muscle, wrapped in flags. - Comment from an article on Antiwar.com (http://antiwar.com) |
#20
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440 volt three phase question
On May 28, 6:31�pm, Tom Horne wrote:
On May 27, 5:22�pm, "Stormin Mormon" wrote: Oh, thank you. I didn't know. -- Christopher A. Young Learn more about Jesus �www.lds.org . "RBM" wrote in message ... �No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected visually. Ie by checking the connections. |
#21
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440 volt three phase question
" I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) How old is this roof top unit... Seriously 440 volts ? Are you sure that it isn't 480 volts ? Right; we should all tighten up our terminology, nominal voltage-wise. It's 120, 240 and 480. *Not* 110, 220 and 440. (Not to mention all those weird older numbers that were used, like 117 volts: WTF did that come from???) *I have found that the actual voltage varies by power company. One company in NJ supplies 460/265 volts while another supplies 480/277. It is quite possible that Stormin is dealing with 440 volts. Don't doubt you at all; however, the *nominal* voltages are still 120/240/480. What you're describing are basically under-voltage situations. *LOL What about 208? |
#22
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440 volt three phase question
On 5/28/2010 3:44 PM, harry wrote:
On May 28, 6:31�pm, Tom wrote: On May 27, 5:22�pm, "Stormin Mormon" wrote: Oh, thank you. I didn't know. -- Christopher A. Young Learn more about Jesus �www.lds.org . wrote in message ... �No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected visually. Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works. |
#23
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440 volt three phase question
More likely, I forgot the number, and typed it wong. I don't deal with
480/3 very often. -- Christopher A. Young Learn more about Jesus www.lds.org .. "John Grabowski" wrote in message ... *I have found that the actual voltage varies by power company. One company in NJ supplies 460/265 volts while another supplies 480/277. It is quite possible that Stormin is dealing with 440 volts. |
#24
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440 volt three phase question
"Stormin Mormon" wrote in message
... I've had the moment to work on 440 volt roof top heating and AC. Once in a while, need some power to run a 120 volt device. Is it 120 volts from one leg to ground? (Yeah, I could just check it. But I was on the roof yesterday, and not sure how long until I get to another roof.) No offense, Stormin, but the fact that you even have to ask such a Q means you have no effing clue about electricity, and thus you proly should not be fooling around with stuff that runs on electricity. Proly missionary work is more your aptitude.... -- EA -- Christopher A. Young Learn more about Jesus www.lds.org . |
#25
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440 volt three phase question
On May 28, 10:55�pm, George wrote:
On 5/28/2010 3:44 PM, harry wrote: On May 28, 6:31 pm, Tom �wrote: On May 27, 5:22 pm, "Stormin Mormon" �wrote: Oh, thank you. I didn't know. -- Christopher A. Young Learn more about Jesus www.lds.org . �wrote in message ... No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected �visually. �Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. |
#26
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440 volt three phase question
So, tell us what's right.
-- Christopher A. Young Learn more about Jesus www.lds.org .. "harry" wrote in message ... You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. |
#27
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440 volt three phase question
On 5/29/2010 3:14 AM, harry wrote:
On May 28, 10:55�pm, wrote: On 5/28/2010 3:44 PM, harry wrote: On May 28, 6:31 pm, Tom �wrote: On May 27, 5:22 pm, "Stormin Mormon" �wrote: Oh, thank you. I didn't know. -- Christopher A. Young Learn more about Jesus www.lds.org . �wrote in message ... No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected �visually. �Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. Really? So if we take the original question where the OP could have used their meter and as an example observed 480 VAC between each phase leg and 277 from each phase leg to neutral we couldn't declare with confidence that the source transformers were connected in "Y" ? |
#28
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440 volt three phase question
On May 29, 12:32�pm, George wrote:
On 5/29/2010 3:14 AM, harry wrote: On May 28, 10:55 pm, �wrote: On 5/28/2010 3:44 PM, harry wrote: On May 28, 6:31 pm, Tom � wrote: On May 27, 5:22 pm, "Stormin Mormon" � wrote: Oh, thank you. I didn't know. -- Christopher A. Young Learn more about Jesus www.lds.org . � wrote in message ... No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected visually. Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. Really? So if we take the original question where the OP could have used their meter and as an example observed 480 VAC between each phase leg and 277 from each phase leg to neutral we couldn't declare with confidence that the source transformers were connected in "Y" ?- Hide quoted text - - Show quoted text - If you read my post, If there are just three line connections brought out, no, you can't tell whether its "star" or "delta" connected. |
#29
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440 volt three phase question
On 5/29/2010 11:08 AM, harry wrote:
On May 29, 12:32�pm, wrote: On 5/29/2010 3:14 AM, harry wrote: On May 28, 10:55 pm, �wrote: On 5/28/2010 3:44 PM, harry wrote: On May 28, 6:31 pm, Tom � wrote: On May 27, 5:22 pm, "Stormin Mormon" � wrote: Oh, thank you. I didn't know. -- Christopher A. Young Learn more about Jesus www.lds.org . � wrote in message ... No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected visually. Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. Really? So if we take the original question where the OP could have used their meter and as an example observed 480 VAC between each phase leg and 277 from each phase leg to neutral we couldn't declare with confidence that the source transformers were connected in "Y" ?- Hide quoted text - - Show quoted text - If you read my post, If there are just three line connections brought out, no, you can't tell whether its "star" or "delta" connected. I did. You didn't describe that limitation but you could still be a long way from completely wrong with only a meter if you only had access to the phase legs. Since a "Y" connection neutral is always bonded to ground I could still get the same readings I described by placing one of the meter probes on ground. |
#30
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440 volt three phase question
In article , George wrote:
On 5/29/2010 11:08 AM, harry wrote: On May 29, 12:32�pm, wrote: On 5/29/2010 3:14 AM, harry wrote: On May 28, 10:55 pm, �wrote: On 5/28/2010 3:44 PM, harry wrote: On May 28, 6:31 pm, Tom � wrote: On May 27, 5:22 pm, "Stormin Mormon" � wrote: Oh, thank you. I didn't know. -- Christopher A. Young Learn more about Jesus www.lds.org . � wrote in message ... No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected visually. Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. Really? So if we take the original question where the OP could have used their meter and as an example observed 480 VAC between each phase leg and 277 from each phase leg to neutral we couldn't declare with confidence that the source transformers were connected in "Y" ?- Hide quoted text - - Show quoted text - If you read my post, If there are just three line connections brought out, no, you can't tell whether its "star" or "delta" connected. I did. You didn't describe that limitation but you could still be a long way from completely wrong with only a meter if you only had access to the phase legs. Since a "Y" connection neutral is always bonded to ground I could still get the same readings I described by placing one of the meter probes on ground. It sounds easy enough for a 440V delta circuit to have all 3 legs measure 277 volts from ground. One way for that to happen is if there is significant and equal stray capacitance from each leg to ground. Another is if someone connects a "Y" load to the circuit, and connects the load's center point to ground. -- - Don Klipstein ) |
#31
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440 volt three phase question
On Sat, 29 May 2010 14:52:54 -0400, George
wrote: On 5/29/2010 11:08 AM, harry wrote: On May 29, 12:32?pm, wrote: On 5/29/2010 3:14 AM, harry wrote: On May 28, 10:55 pm, ?wrote: On 5/28/2010 3:44 PM, harry wrote: On May 28, 6:31 pm, Tom ? wrote: On May 27, 5:22 pm, "Stormin Mormon" ? wrote: Oh, thank you. I didn't know. -- Christopher A. Young Learn more about Jesus www.lds.org . ? wrote in message ... No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected visually. Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. Really? So if we take the original question where the OP could have used their meter and as an example observed 480 VAC between each phase leg and 277 from each phase leg to neutral we couldn't declare with confidence that the source transformers were connected in "Y" ?- Hide quoted text - - Show quoted text - If you read my post, If there are just three line connections brought out, no, you can't tell whether its "star" or "delta" connected. I did. You didn't describe that limitation but you could still be a long way from completely wrong with only a meter if you only had access to the phase legs. Since a "Y" connection neutral is always bonded to ground I could still get the same readings I described by placing one of the meter probes on ground. If I was unsure of the voltage, what I would do is call maintenance and ask. |
#32
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440 volt three phase question
No, it's 220 more or less, to ground
It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected visually. Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. Really? So if we take the original question where the OP could have used their meter and as an example observed 480 VAC between each phase leg and 277 from each phase leg to neutral we couldn't declare with confidence that the source transformers were connected in "Y" ?- Hide quoted text - - Show quoted text - If you read my post, If there are just three line connections brought out, no, you can't tell whether its "star" or "delta" connected. I did. You didn't describe that limitation but you could still be a long way from completely wrong with only a meter if you only had access to the phase legs. Since a "Y" connection neutral is always bonded to ground I could still get the same readings I described by placing one of the meter probes on ground. If I was unsure of the voltage, what I would do is call maintenance and ask. *As I recall on a delta connection one of the phases will have a higher reading to ground than the other two. On a Y connection the reading to ground will be the same. In NJ, Public Service Electric and Gas will not permit that high leg to be installed in the same panel as the neutral. The NEC allows it though. |
#33
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440 volt three phase question
On 5/29/2010 5:01 PM, John Grabowski wrote:
No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected visually. Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. Really? So if we take the original question where the OP could have used their meter and as an example observed 480 VAC between each phase leg and 277 from each phase leg to neutral we couldn't declare with confidence that the source transformers were connected in "Y" ?- Hide quoted text - - Show quoted text - If you read my post, If there are just three line connections brought out, no, you can't tell whether its "star" or "delta" connected. I did. You didn't describe that limitation but you could still be a long way from completely wrong with only a meter if you only had access to the phase legs. Since a "Y" connection neutral is always bonded to ground I could still get the same readings I described by placing one of the meter probes on ground. If I was unsure of the voltage, what I would do is call maintenance and ask. *As I recall on a delta connection one of the phases will have a higher reading to ground than the other two. On a Y connection the reading to ground will be the same. In NJ, Public Service Electric and Gas will not permit that high leg to be installed in the same panel as the neutral. The NEC allows it though. That is because of the way the power company arranges that type of service. One of the transformers used in the delta connection has a center tap. They did that it situations where most of the load would be 3 phase but the same service could still supply 120 general purpose loads without the need for an on premise transformer. |
#34
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440 volt three phase question
No, it's 220 more or less, to ground
It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected visually. Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. Really? So if we take the original question where the OP could have used their meter and as an example observed 480 VAC between each phase leg and 277 from each phase leg to neutral we couldn't declare with confidence that the source transformers were connected in "Y" ?- Hide quoted text - - Show quoted text - If you read my post, If there are just three line connections brought out, no, you can't tell whether its "star" or "delta" connected. I did. You didn't describe that limitation but you could still be a long way from completely wrong with only a meter if you only had access to the phase legs. Since a "Y" connection neutral is always bonded to ground I could still get the same readings I described by placing one of the meter probes on ground. If I was unsure of the voltage, what I would do is call maintenance and ask. *As I recall on a delta connection one of the phases will have a higher reading to ground than the other two. On a Y connection the reading to ground will be the same. In NJ, Public Service Electric and Gas will not permit that high leg to be installed in the same panel as the neutral. The NEC allows it though. That is because of the way the power company arranges that type of service. One of the transformers used in the delta connection has a center tap. They did that it situations where most of the load would be 3 phase but the same service could still supply 120 general purpose loads without the need for an on premise transformer. *So a volt meter will tell you if the service is a delta or a Y. |
#35
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440 volt three phase question
In article , John Grabowski wrote:
*As I recall on a delta connection one of the phases will have a higher reading to ground than the other two. On a Y connection the reading to ground will be the same. In NJ, Public Service Electric and Gas will not permit that high leg to be installed in the same panel as the neutral. The NEC allows it though. What you are describing sounds to me like a 240V "star" system with high leg, a variant of Y. Two of the phases are 240V center tap with the center tap connected to neutral. That provides four 120V legs. The third is 240V with one end rather than the center tap of that transformer's winding connected to neutral to provide the "high leg". It is possible to use the center tap of that to provide a fifth 120V leg. -- - Don Klipstein ) |
#36
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440 volt three phase question
*As I recall on a delta connection one of the phases will have a higher reading to ground than the other two. On a Y connection the reading to ground will be the same. In NJ, Public Service Electric and Gas will not permit that high leg to be installed in the same panel as the neutral. The NEC allows it though. What you are describing sounds to me like a 240V "star" system with high leg, a variant of Y. Two of the phases are 240V center tap with the center tap connected to neutral. That provides four 120V legs. The third is 240V with one end rather than the center tap of that transformer's winding connected to neutral to provide the "high leg". It is possible to use the center tap of that to provide a fifth 120V leg. *It's been a while since I have worked on three phase, but I seem to recall on a three phase 240 volt delta system, the high (Orange) leg is around 180 volts to ground. I only remember one phase as being center tapped. Next time I meet with someone from the power company I will ask them to refresh my memory. |
#37
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440 volt three phase question
*As I recall on a delta connection one of the phases will have a higher
reading to ground than the other two. On a Y connection the reading to ground will be the same. In NJ, Public Service Electric and Gas will not permit that high leg to be installed in the same panel as the neutral. The NEC allows it though. What you are describing sounds to me like a 240V "star" system with high leg, a variant of Y. Two of the phases are 240V center tap with the center tap connected to neutral. That provides four 120V legs. The third is 240V with one end rather than the center tap of that transformer's winding connected to neutral to provide the "high leg". It is possible to use the center tap of that to provide a fifth 120V leg. *It's been a while since I have worked on three phase, but I seem to recall on a three phase 240 volt delta system, the high (Orange) leg is around 180 volts to ground. I only remember one phase as being center tapped. Next time I meet with someone from the power company I will ask them to refresh my memory. *I was just looking in my PSE&G handbook and found a drawing for three phase services. They supply 3 phase 4 wire 120/240 volt delta, 3 phase 4 wire 120/208 volt wye, 3 phase 4 wire 277/480 volt wye services and they also list 3 phase 4 wire 265/460 volt wye but in parentheses they have "Obsolete". I guess the 460 is being or has been phased out (No pun intended). For the delta service they want the orange leg on the right terminal in the meter and of course after that it must go on the center terminal as per the NEC. As I mentioned before PSE&G wants the neutral in a separate panel from the high leg, therefore two panels must be installed; one single phase with neutral and one three phase without neutral. I think JCP&L will accept the neutral and high leg together, but I would have to double check. |
#38
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440 volt three phase question
On May 29, 7:52�pm, George wrote:
On 5/29/2010 11:08 AM, harry wrote: On May 29, 12:32 pm, �wrote: On 5/29/2010 3:14 AM, harry wrote: On May 28, 10:55 pm, � wrote: On 5/28/2010 3:44 PM, harry wrote: On May 28, 6:31 pm, Tom � wrote: On May 27, 5:22 pm, "Stormin Mormon" � wrote: Oh, thank you. I didn't know. -- Christopher A. Young Learn more about Jesus www.lds.org . � wrote in message ... No, it's 220 more or less, to ground It is entirely possible that the 440 volts is from a delta configured transformer that is not ground referenced or is corner grounded. Point is that one shouldn't assume that the transformer that is supplying the current is Y configured. -- Tom Horne It's only possible to determine how a three phase transformer is connected visually. Ie by checking the connections. You can make a very reliable determination with just a meter and knowing how 3 phase AC works.- Hide quoted text - - Show quoted text - That is completely wrong. Really? So if we take the original question where the OP could have used their meter and as an example observed 480 VAC between each phase leg and 277 from each phase leg to neutral we couldn't declare with confidence that the source transformers were connected in "Y" ?- Hide quoted text - - Show quoted text - If you read my post, If there are just three line �connections brought out, no, you can't tell whether its "star" or "delta" connected. I did. You didn't describe that limitation but you could still be a long way from completely wrong with only a meter if you only had access to the phase legs. Since a "Y" connection neutral is always bonded to ground I could still get the same readings I described by placing one of the meter probes on ground.- Hide quoted text - - Show quoted text - But you still wouldn't know whether it was star or delta connected. |
#39
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440 volt three phase question
On May 29, 11:29�pm, (Don Klipstein) wrote:
In article , John Grabowski wrote: *As I recall on a delta connection one of the phases will have a higher reading to ground than the other two. �On a Y connection the reading to ground will be the same. �In NJ, Public Service Electric and Gas will not permit that high leg to be installed in the same panel as the neutral. � The NEC allows it though. � What you are describing sounds to me like a 240V "star" system with high leg, a variant of Y. �Two of the phases are 240V center tap with the center tap connected to neutral. �That provides four 120V legs. �The third is 240V with one end rather than the center tap of that transformer's winding connected to neutral to provide the "high leg". �It is possible to use the center tap of that to provide a fifth 120V leg. -- �- Don Klipstein ) What you are describing is called a zig zag connected transformer, common in the US but rarely used in the UK except for producing a phase shift for rectification purposes. (DC output more ripple free ) http://www.langlois-france.com/pdf/ZIG-GB.pdf |
#40
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440 volt three phase question
In article , John Grabowski wrote:
*As I recall on a delta connection one of the phases will have a higher reading to ground than the other two. On a Y connection the reading to ground will be the same. In NJ, Public Service Electric and Gas will not permit that high leg to be installed in the same panel as the neutral. The NEC allows it though. What you are describing sounds to me like a 240V "star" system with high leg, a variant of Y. Two of the phases are 240V center tap with the center tap connected to neutral. That provides four 120V legs. The third is 240V with one end rather than the center tap of that transformer's winding connected to neutral to provide the "high leg". It is possible to use the center tap of that to provide a fifth 120V leg. *It's been a while since I have worked on three phase, but I seem to recall on a three phase 240 volt delta system, the high (Orange) leg is around 180 volts to ground. I only remember one phase as being center tapped. Next time I meet with someone from the power company I will ask them to refresh my memory. A 240V phase-to-phase delta with grounded of center tap of one of the three transformer windings feeding it would have its "high leg" at 208V from "neutral", same as 120V "leg-to-ground" "Y" or "star" having any "leg" of this being 208V from a leg one phase apart. Furthermore, a "delta" source can power a "Y" load unless the source to the load has neutral disagreeing with a delta's neutral being connected to center tap of one of the 3 feeding transformer windings. And a "Y" source can power a "delta" load. These compatibilities are qualified by compatibility in voltage leg-to-leg, or "phase-to-phase", which I consider to be more of a notation for "delta" and less for "Wye". Furthermore, I have seen some preference for 3-phase power to be delivered from a source in form of delta without neutral connected to any point of the 3 feeding transformers' windings when there is lack of need for anything else. The reasoning is that failing-open of one of the 3 same-level-upstream transformer windings only reduces how much power can be delivered, with little to no compromise otherwise in ability to use all 3 phases. -- - Don Klipstein ) |
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