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Converting 3-phase to single phase with resilience
I suspect this isn't possible, but I thought I'd ask just in case...
I've got a large office with a 3-phase electrical supply. But I don't have any 3-phase equipment; I split the 3 phases to 3 x single phase sub-mains feeding CUs on each floor. The original building has a 3x60A supply, but that was upgraded to a 3x100A supply about five years ago. I don't think our total draw ever exceeds 100A, so in theory we could operate from just one of the phases. We have regular power outages, all of which are acknowledged by UK power networks and normally involve some sort of problem at a substation. But strangely they don't always affect all three phases. Hence my question: Is there a way to convert a three-phase supply to some sort of redundant single-phase supply? I wouldn't want something that involves power-loss, as the 3-phase supply comes into the basement and I don't have any easy way of getting rid of heat from there; but even some sort of "throw the switch Igor" switchover solution would be better than I've got at the moment when I end up losing a random floor (and typically the CH boiler as well, which means we need to close the office when it gets too cold). |
Converting 3-phase to single phase with resilience
Caecilius laid this down on his screen :
Is there a way to convert a three-phase supply to some sort of redundant single-phase supply? It should be possible to have (3x) interlocked contactors installed, so that only one could be active and providing the entire supply, at anyone time and to the entire building. That should make it possible for it to sequence, through the phases should one drop out. I have never seen or heard of it being done, but it is certainly practical to do. There would be a short interruption in the supply, during the switch over. Best talk to the technical department of your supplier about the possibilities. You would still be paying for the 3x supplies, despite only using one at any time. |
Converting 3-phase to single phase with resilience
On Friday, 20 January 2017 18:33:13 UTC, Caecilius wrote:
I suspect this isn't possible, but I thought I'd ask just in case... I've got a large office with a 3-phase electrical supply. But I don't have any 3-phase equipment; I split the 3 phases to 3 x single phase sub-mains feeding CUs on each floor. The original building has a 3x60A supply, but that was upgraded to a 3x100A supply about five years ago. I don't think our total draw ever exceeds 100A, so in theory we could operate from just one of the phases. We have regular power outages, all of which are acknowledged by UK power networks and normally involve some sort of problem at a substation. But strangely they don't always affect all three phases. Hence my question: Is there a way to convert a three-phase supply to some sort of redundant single-phase supply? I wouldn't want something that involves power-loss, as the 3-phase supply comes into the basement and I don't have any easy way of getting rid of heat from there; but even some sort of "throw the switch Igor" switchover solution would be better than I've got at the moment when I end up losing a random floor (and typically the CH boiler as well, which means we need to close the office when it gets too cold). Relays or rather contactors could do this easily. But do you need (to pay for) a 3 phase supply? NT |
Converting 3-phase to single phase with resilience
It does seem strange to me that power outages are often enough to be a
problem. Maybe the infrastructure where you are needs some serious work. Might be an idea to see how many locals this affects and get on to the power network people to fix it properly rather than messing around with the supply. After all in my road the phases are fed to alternate houses so if this did happen a lot every third house would lose power, and they don't. Brian -- ----- - This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please! "Harry Bloomfield" wrote in message ... Caecilius laid this down on his screen : Is there a way to convert a three-phase supply to some sort of redundant single-phase supply? It should be possible to have (3x) interlocked contactors installed, so that only one could be active and providing the entire supply, at anyone time and to the entire building. That should make it possible for it to sequence, through the phases should one drop out. I have never seen or heard of it being done, but it is certainly practical to do. There would be a short interruption in the supply, during the switch over. Best talk to the technical department of your supplier about the possibilities. You would still be paying for the 3x supplies, despite only using one at any time. |
Converting 3-phase to single phase with resilience
On Friday, 20 January 2017 18:33:13 UTC, Caecilius wrote:
I suspect this isn't possible, but I thought I'd ask just in case... I've got a large office with a 3-phase electrical supply. But I don't have any 3-phase equipment; I split the 3 phases to 3 x single phase sub-mains feeding CUs on each floor. The original building has a 3x60A supply, but that was upgraded to a 3x100A supply about five years ago. I don't think our total draw ever exceeds 100A, so in theory we could operate from just one of the phases. We have regular power outages, all of which are acknowledged by UK power networks and normally involve some sort of problem at a substation. But strangely they don't always affect all three phases. Hence my question: Is there a way to convert a three-phase supply to some sort of redundant single-phase supply? I wouldn't want something that involves power-loss, as the 3-phase supply comes into the basement and I don't have any easy way of getting rid of heat from there; but even some sort of "throw the switch Igor" switchover solution would be better than I've got at the moment when I end up losing a random floor (and typically the CH boiler as well, which means we need to close the office when it gets too cold). All you need is three contactors and a single pole, three way (rotary?) switch. http://www.ebay.co.uk/bhp/rotary-switch It would be ideal if they were also mechanically interlocked. |
Converting 3-phase to single phase with resilience
On Friday, 20 January 2017 18:33:13 UTC, Caecilius wrote:
I suspect this isn't possible, but I thought I'd ask just in case... I've got a large office with a 3-phase electrical supply. But I don't have any 3-phase equipment; I split the 3 phases to 3 x single phase sub-mains feeding CUs on each floor. The original building has a 3x60A supply, but that was upgraded to a 3x100A supply about five years ago. I don't think our total draw ever exceeds 100A, so in theory we could operate from just one of the phases. We have regular power outages, all of which are acknowledged by UK power networks and normally involve some sort of problem at a substation. But strangely they don't always affect all three phases. Hence my question: Is there a way to convert a three-phase supply to some sort of redundant single-phase supply? I wouldn't want something that involves power-loss, as the 3-phase supply comes into the basement and I don't have any easy way of getting rid of heat from there; but even some sort of "throw the switch Igor" switchover solution would be better than I've got at the moment when I end up losing a random floor (and typically the CH boiler as well, which means we need to close the office when it gets too cold). A reversing switch for a three phase motor could probably be modified. |
Converting 3-phase to single phase with resilience
harry used his keyboard to write :
It would be ideal if they were also mechanically interlocked. I would suggest both electrical and mechanical interlocking are essential. |
Converting 3-phase to single phase with resilience
On 20-Jan-17 6:33 PM, Caecilius wrote:
I suspect this isn't possible, but I thought I'd ask just in case... I've got a large office with a 3-phase electrical supply. But I don't have any 3-phase equipment; I split the 3 phases to 3 x single phase sub-mains feeding CUs on each floor. The original building has a 3x60A supply, but that was upgraded to a 3x100A supply about five years ago. I don't think our total draw ever exceeds 100A, so in theory we could operate from just one of the phases. We have regular power outages, all of which are acknowledged by UK power networks and normally involve some sort of problem at a substation. But strangely they don't always affect all three phases. Hence my question: Is there a way to convert a three-phase supply to some sort of redundant single-phase supply? I wouldn't want something that involves power-loss, as the 3-phase supply comes into the basement and I don't have any easy way of getting rid of heat from there; but even some sort of "throw the switch Igor" switchover solution would be better than I've got at the moment when I end up losing a random floor (and typically the CH boiler as well, which means we need to close the office when it gets too cold). How about three double throw contactors, each powered by one phase and wired so that it passes that phase through to its associated CU when powered, but switches to another phase when the power fails? It should work completely automatically, with minimum down time, and they shouldn't draw enough power to cause you heat gain problems. If you want to allow for the possibility of two out of three phases failing, a second contactor in series after the first and powered by the output from the first would allow you to switch in the phase that isn't connected to either pole of the first if both of those fail. -- -- Colin Bignell |
Converting 3-phase to single phase with resilience
On Sat, 21 Jan 2017 08:45:04 -0000, "Brian Gaff"
wrote: It does seem strange to me that power outages are often enough to be a problem. Maybe the infrastructure where you are needs some serious work. Might be an idea to see how many locals this affects and get on to the power network people to fix it properly rather than messing around with the supply. After all in my road the phases are fed to alternate houses so if this did happen a lot every third house would lose power, and they don't. Brian Strange it may be, but it keeps happening. The power was out for the best part of two days this week in two seperate outages. The UK power networks engineer said that they'd finally worked out the problem, which was apparently caused by two substations being linked when no such link was shown on the map. But we've had promises of "it's all fixed now" for a few years, and each year there's one or two months with outages. |
Converting 3-phase to single phase with resilience
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Converting 3-phase to single phase with resilience
In article , Caecilius
wrote: On Sat, 21 Jan 2017 08:45:04 -0000, "Brian Gaff" wrote: It does seem strange to me that power outages are often enough to be a problem. Maybe the infrastructure where you are needs some serious work. Might be an idea to see how many locals this affects and get on to the power network people to fix it properly rather than messing around with the supply. After all in my road the phases are fed to alternate houses so if this did happen a lot every third house would lose power, and they don't. Brian Strange it may be, but it keeps happening. The power was out for the best part of two days this week in two seperate outages. The UK power networks engineer said that they'd finally worked out the problem, which was apparently caused by two substations being linked when no such link was shown on the map. That could be a problem with copied maps, when the copying was done by tracing the old one. Short links did get misses. When I was with SESEB (getting on for 60 years ago), one customer wanted to upgrade to a 3 phase supply - but the maps showed he had no supply at all. -- from KT24 in Surrey, England |
Converting 3-phase to single phase with resilience
On Sat, 21 Jan 2017 09:56:35 +0000, Nightjar
wrote: On 20-Jan-17 6:33 PM, Caecilius wrote: I suspect this isn't possible, but I thought I'd ask just in case... I've got a large office with a 3-phase electrical supply. But I don't have any 3-phase equipment; I split the 3 phases to 3 x single phase sub-mains feeding CUs on each floor. The original building has a 3x60A supply, but that was upgraded to a 3x100A supply about five years ago. I don't think our total draw ever exceeds 100A, so in theory we could operate from just one of the phases. We have regular power outages, all of which are acknowledged by UK power networks and normally involve some sort of problem at a substation. But strangely they don't always affect all three phases. Hence my question: Is there a way to convert a three-phase supply to some sort of redundant single-phase supply? I wouldn't want something that involves power-loss, as the 3-phase supply comes into the basement and I don't have any easy way of getting rid of heat from there; but even some sort of "throw the switch Igor" switchover solution would be better than I've got at the moment when I end up losing a random floor (and typically the CH boiler as well, which means we need to close the office when it gets too cold). How about three double throw contactors, each powered by one phase and wired so that it passes that phase through to its associated CU when powered, but switches to another phase when the power fails? It should work completely automatically, with minimum down time, and they shouldn't draw enough power to cause you heat gain problems. If you want to allow for the possibility of two out of three phases failing, a second contactor in series after the first and powered by the output from the first would allow you to switch in the phase that isn't connected to either pole of the first if both of those fail. Thanks. That sounds like it might work. I'll sketch it out and see if it's workable. |
Converting 3-phase to single phase with resilience
On 21/01/2017 08:45, Brian Gaff wrote:
It does seem strange to me that power outages are often enough to be a problem. Maybe the infrastructure where you are needs some serious work. Might be an idea to see how many locals this affects and get on to the power network people to fix it properly rather than messing around with the supply. After all in my road the phases are fed to alternate houses so if this did happen a lot every third house would lose power, and they don't. Brian I currently have 3-phase issues at the shop. 1 phase is down on voltage, the 2nd which we were connected to started browning out randomly a few years back so we were switched to the 3rd phase which has now started breaking down giving intermittent voltage drops. A fault has been identified as 5m from shop but to fix it means knocking out all the shops/flats in the row which they aren't keen on doing but it's now been escalated to the fat-controller (I think that's who he said) for planning apparently.. |
Converting 3-phase to single phase with resilience
Brian Gaff submitted this idea :
Sounds like you need a very big changeover switch break before make three way! I cannot see how you could easily make this automatic or combine them considering the phase shift involved. Its no biggie to arrange, phase shift has nothing to do with it as only a single phase is needed at any one time. |
Converting 3-phase to single phase with resilience
On 21/01/2017 09:56, Nightjar wrote:
On 20-Jan-17 6:33 PM, Caecilius wrote: I suspect this isn't possible, but I thought I'd ask just in case... I've got a large office with a 3-phase electrical supply. But I don't have any 3-phase equipment; I split the 3 phases to 3 x single phase sub-mains feeding CUs on each floor. The original building has a 3x60A supply, but that was upgraded to a 3x100A supply about five years ago. I don't think our total draw ever exceeds 100A, so in theory we could operate from just one of the phases. We have regular power outages, all of which are acknowledged by UK power networks and normally involve some sort of problem at a substation. But strangely they don't always affect all three phases. Hence my question: Is there a way to convert a three-phase supply to some sort of redundant single-phase supply? I wouldn't want something that involves power-loss, as the 3-phase supply comes into the basement and I don't have any easy way of getting rid of heat from there; but even some sort of "throw the switch Igor" switchover solution would be better than I've got at the moment when I end up losing a random floor (and typically the CH boiler as well, which means we need to close the office when it gets too cold). How about three double throw contactors, each powered by one phase and wired so that it passes that phase through to its associated CU when powered, but switches to another phase when the power fails? I like that idea. -- Adam |
Converting 3-phase to single phase with resilience
It happens that Caecilius formulated :
Thanks. That sounds like it might work. I'll sketch it out and see if it's workable. Be very aware that contacts can and do sometimes weld up, so mechanical interlocking is essential. |
Converting 3-phase to single phase with resilience
On 22-Jan-17 1:06 PM, Harry Bloomfield wrote:
It happens that Caecilius formulated : Thanks. That sounds like it might work. I'll sketch it out and see if it's workable. Be very aware that contacts can and do sometimes weld up, so mechanical interlocking is essential. What should be interlocked? The whole idea of the setup is that each contactor operates separately from the others. -- -- Colin Bignell |
Converting 3-phase to single phase with resilience
Nightjar wrote:
On 22-Jan-17 1:06 PM, Harry Bloomfield wrote: It happens that Caecilius formulated : Thanks. That sounds like it might work. I'll sketch it out and see if it's workable. Be very aware that contacts can and do sometimes weld up, so mechanical interlocking is essential. What should be interlocked? The whole idea of the setup is that each contactor operates separately from the others. The potential hazard is that if the main contacts on one of the contactors weld closed, then the system closes another contactor, it thus creates a potential phase-phase connection. If the contactor has auxiliary contacts, so long as their state mirrors the main contacts if they are welded, then the safety interlocking can be electrical. Chris -- Chris J Dixon Nottingham UK Plant amazing Acers. |
Converting 3-phase to single phase with resilience
Chris J Dixon formulated the question :
The potential hazard is that if the main contacts on one of the contactors weld closed, then the system closes another contactor, it thus creates a potential phase-phase connection. If the contactor has auxiliary contacts, so long as their state mirrors the main contacts if they are welded, then the safety interlocking can be electrical. Exactly! I would also want to provide some mechanical interlocking too, to be certain it never could happen. I have come across mechanical interlocking on star/delta motor starter systems, so I know it can be done. |
Converting 3-phase to single phase with resilience
On 23-Jan-17 10:20 AM, Chris J Dixon wrote:
Nightjar wrote: On 22-Jan-17 1:06 PM, Harry Bloomfield wrote: It happens that Caecilius formulated : Thanks. That sounds like it might work. I'll sketch it out and see if it's workable. Be very aware that contacts can and do sometimes weld up, so mechanical interlocking is essential. What should be interlocked? The whole idea of the setup is that each contactor operates separately from the others. The potential hazard is that if the main contacts on one of the contactors weld closed, then the system closes another contactor, it thus creates a potential phase-phase connection... How? These are independent single pole changeover contactors, with the common of one contactor connected to only one CU. One contactor closing does not create a connection to the output of any other. -- -- Colin Bignell |
Converting 3-phase to single phase with resilience
In article ,
Harry Bloomfield wrote: Chris J Dixon formulated the question : The potential hazard is that if the main contacts on one of the contactors weld closed, then the system closes another contactor, it thus creates a potential phase-phase connection. If the contactor has auxiliary contacts, so long as their state mirrors the main contacts if they are welded, then the safety interlocking can be electrical. Exactly! I would also want to provide some mechanical interlocking too, to be certain it never could happen. I have come across mechanical interlocking on star/delta motor starter systems, so I know it can be done. I was brought up on Castek Keys -- from KT24 in Surrey, England |
Converting 3-phase to single phase with resilience
charles brought next idea :
I was brought up on Castek Keys As was I. |
Converting 3-phase to single phase with resilience
On 23/01/2017 09:30, Nightjar wrote:
On 22-Jan-17 1:06 PM, Harry Bloomfield wrote: It happens that Caecilius formulated : Thanks. That sounds like it might work. I'll sketch it out and see if it's workable. Be very aware that contacts can and do sometimes weld up, so mechanical interlocking is essential. What should be interlocked? The whole idea of the setup is that each contactor operates separately from the others. +1 -- Adam |
Converting 3-phase to single phase with resilience
On 21/01/2017 10:50, Caecilius wrote:
On Sat, 21 Jan 2017 09:56:35 +0000, Nightjar wrote: On 20-Jan-17 6:33 PM, Caecilius wrote: How about three double throw contactors, each powered by one phase and wired so that it passes that phase through to its associated CU when powered, but switches to another phase when the power fails? It should work completely automatically, with minimum down time, and they shouldn't draw enough power to cause you heat gain problems. If you want to allow for the possibility of two out of three phases failing, a second contactor in series after the first and powered by the output from the first would allow you to switch in the phase that isn't connected to either pole of the first if both of those fail. Thanks. That sounds like it might work. I'll sketch it out and see if it's workable. Do short power outages cause trouble for your PCs etc or are you using UPS? -- Adam |
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