Posted: 3/11/2016 1:16:58 AM EDT
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I have 240vac 3ph incoming power - 3 wire delta. I've had some issues w/ our power company recently that has caused equipment damage, last month they lost a fuse down the road and it wasted parts in one of my cnc machines. I fixed it, and moved on... Today one of my Kitamura's threw a fault on Z axis, then a few seconds later 4 more power related errors and I smelled plastic smores....
Checked incoming voltage at the main - 240 phase to phase. But phase to ground is fucked up I think... 2 legs are 240 phase to ground, and one is zero volts.... Normally I thought it was supposed to be 120v phase to ground on each leg right? I am not 208 high leg delta. My other shop across the road has about 220vac incoming power, same 3 wire delta, and each leg is 120v phase to ground.... The fug is going on? |
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First- you may have a corner grounded Delta, where one of the phases is grounded. So if you measure between the phase and ground on the grounded leg you will get 0 vo!ts. This is an old system, but still around. This had to be done on a Delta secondary transformer if there was no center tap for a high leg- which would be 208 to ground instead of 120. The system has to be grounded, and grounding a leg was how to do it. Or you lost phase. Measure phase to phase between a good phase and the one with 0 to ground. If you have 240, you didn't lose a phase. If you don't have 240, you lost that phase. Reading 240-ground on 2 phases pretty much confirms you have. Your ground is bolted to a phase in the trans, your reading of 0 on one phase is correct Losing a phase would make any motors or equiment single phase, without any type of protection could cause problems. I would think expensive equipment though would have phase detection, but I'm sure a lot of it doesn't. You sure your other shop isn't a y system? If it's Delta, it would have a high leg, or one of the legs to ground would read 0. You said about 220, the y version of 120/240 is actually 120/208. It sounds like you might have a y system.. I take it the shop with problems has no neutral. ETA- Where abouts in PA are you OP. I'm in southern PA area if you're close I could check it for you and let you know what you got. |
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I have 240vac 3ph incoming power - 3 wire delta. I've had some issues w/ our power company recently that has caused equipment damage, last month they lost a fuse down the road and it wasted parts in one of my cnc machines. I fixed it, and moved on... Today one of my Kitamura's threw a fault on Z axis, then a few seconds later 4 more power related errors and I smelled plastic smores.... Checked incoming voltage at the main - 240 phase to phase. But phase to ground is fucked up I think... 2 legs are 240 phase to ground, and one is zero volts.... Normally I thought it was supposed to be 120v phase to ground on each leg right? I am not 208 high leg delta. My other shop across the road has about 220vac incoming power, same 3 wire delta, and each leg is 120v phase to ground.... The fug is going on? If all 3 phase readings are 240 phase to phase, that checks OK No That is as it should be. Does the branch circuit readings phase to phase and phases to ground at the cnc machine also check good like the "mains"? (I'm assuming you checked the "mains" at the service panel.) If so, you have a machine controller problem. The damage could have been caused by a short time surge or other disruption with the power now back to normal. |
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Power company here today. There is definitely an issue. Says that there is a problem at the transformer and that we are missing a leg. Somehow the other voltage is backfeeding somewhere to make it appear we have 3 legs?? Is that possible?
Anyway they're up on the pole fucking around right now. I need to look into line protection for my machines. I am not familiar with it - are those local devices in each machine or is it run somewhere at the main incoming power? |
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Power company here today. There is definitely an issue. Says that there is a problem at the transformer and that we are missing a leg. Somehow the other voltage is backfeeding somewhere to make it appear we have 3 legs?? Is that possible? Anyway they're up on the pole fucking around right now. I need to look into line protection for my machines. I am not familiar with it - are those local devices in each machine or is it run somewhere at the main incoming power? There are phase monitors that will open a contactor on fault conditions. Lost phase, incorrect rotation, and also ground fault monitors. Installation would probably be expensive but seems like cheap insurance. Speaking of insurance, your insurer might go after the power company for damages if you file a claim. Some of your losses covered, power company gets serious about finding the problem. Also you might consider installing a line monitor to document what's going on, both to enable a solution and support a claim. |
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yes it is. you could spend the rest of your life playing with it. Quoted:
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Electrical work is not a hobby. Call a qualified electrician......... yes it is. you could spend the rest of your life playing with it. How long that is... depends on how good you are. 
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Quoted: Power company here today. There is definitely an issue. Says that there is a problem at the transformer and that we are missing a leg. Somehow the other voltage is backfeeding somewhere to make it appear we have 3 legs?? Is that possible? Anyway they're up on the pole fucking around right now. I need to look into line protection for my machines. I am not familiar with it - are those local devices in each machine or is it run somewhere at the main incoming power? |
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I use these products extensively, best bang for your buck. http://symcom.com |
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How long that is... depends on how good you are. Quoted:
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Electrical work is not a hobby. Call a qualified electrician......... yes it is. you could spend the rest of your life playing with it. How long that is... depends on how good you are. I hear Darwin Electrical has some very good reviews, shockingly good as a matter of fact..... 
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240 phase to ground with a dead leg? You have a ground fault on that dead leg. Somewhere the dead leg is going to ground. That is a major safety issue and will also cook your electronics. Yep and that it did. Plastic smores for everyone! It's coming from their transformers on the pole. Lineman here just confirmed it is NOT a corner grounded system. Essentially we have an Open Primary Neutral Y 4-line primary. Then a 240V delta secondary 3-wire. It should have voltage to ground equal on all legs. |
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Yep and that it did. Plastic smores for everyone! It's coming from their transformers on the pole. Lineman here just confirmed it is NOT a corner grounded system. Essentially we have an Open Primary Neutral Y 4-line primary. Then a 240V delta secondary 3-wire. It should have voltage to ground equal on all legs. Quoted:
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240 phase to ground with a dead leg? You have a ground fault on that dead leg. Somewhere the dead leg is going to ground. That is a major safety issue and will also cook your electronics. Yep and that it did. Plastic smores for everyone! It's coming from their transformers on the pole. Lineman here just confirmed it is NOT a corner grounded system. Essentially we have an Open Primary Neutral Y 4-line primary. Then a 240V delta secondary 3-wire. It should have voltage to ground equal on all legs. It should, but you have one leg going to ground. That is the dead leg. That is also why your readings on the other two legs are reading from phase to ground what you should be reading phase to phase. |
| I feel your pain MBX, I had similar issues in a building I leased when I first started my shop. There was a pre-formed concrete plant behind me on the same branch line that would brown out then spike the entire area occasionally. One of my machines lost the spindle motor and controller, the Fanuc controlled machines survived miraculously but the Mitsubishi controls did not. |
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I feel your pain MBX, I had similar issues in a building I leased when I first started my shop. There was a pre-formed concrete plant behind me on the same branch line that would brown out then spike the entire area occasionally. One of my machines lost the spindle motor and controller, the Fanuc controlled machines survived miraculously but the Mitsubishi controls did not. Both of my Kiti machines were powered up, along with my waterjet and a Tig welder. One of the Kiti's smoked and threw a bunch of errors. The other didn't flinch - both Fanuc controls. The waterjet was on but not running, seems ok. The Tig welder - made some really poopy welds. Doesn't smell burnt but we'll see once we get power back out there. We also lost a power supply on a Fanuc Robot....just powered it up and it blew....we thought it was a bad power supply until everything else happened... |
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If all 3 phase readings are 240 phase to phase, that checks OK No That is as it should be. Does the branch circuit readings phase to phase and phases to ground at the cnc machine also check good like the "mains"? (I'm assuming you checked the "mains" at the service panel.) If so, you have a machine controller problem. The damage could have been caused by a short time surge or other disruption with the power now back to normal. Quoted:
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I have 240vac 3ph incoming power - 3 wire delta. I've had some issues w/ our power company recently that has caused equipment damage, last month they lost a fuse down the road and it wasted parts in one of my cnc machines. I fixed it, and moved on... Today one of my Kitamura's threw a fault on Z axis, then a few seconds later 4 more power related errors and I smelled plastic smores.... Checked incoming voltage at the main - 240 phase to phase. But phase to ground is fucked up I think... 2 legs are 240 phase to ground, and one is zero volts.... Normally I thought it was supposed to be 120v phase to ground on each leg right? I am not 208 high leg delta. My other shop across the road has about 220vac incoming power, same 3 wire delta, and each leg is 120v phase to ground.... The fug is going on? If all 3 phase readings are 240 phase to phase, that checks OK No That is as it should be. Does the branch circuit readings phase to phase and phases to ground at the cnc machine also check good like the "mains"? (I'm assuming you checked the "mains" at the service panel.) If so, you have a machine controller problem. The damage could have been caused by a short time surge or other disruption with the power now back to normal. Delta systems can be corner grounded, grounded at the mid point of one winding or not grounded at all. You have a corner grounded delta and your voltage values are correct. A corner grounded system does not have a neutral. The stinger on a mid point grounded delta would be close to 208 with 120 phase-ground/neutral on the other two phases. |
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Both of my Kiti machines were powered up, along with my waterjet and a Tig welder. One of the Kiti's smoked and threw a bunch of errors. The other didn't flinch - both Fanuc controls. The waterjet was on but not running, seems ok. The Tig welder - made some really poopy welds. Doesn't smell burnt but we'll see once we get power back out there. We also lost a power supply on a Fanuc Robot....just powered it up and it blew....we thought it was a bad power supply until everything else happened... Quoted:
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I feel your pain MBX, I had similar issues in a building I leased when I first started my shop. There was a pre-formed concrete plant behind me on the same branch line that would brown out then spike the entire area occasionally. One of my machines lost the spindle motor and controller, the Fanuc controlled machines survived miraculously but the Mitsubishi controls did not. Both of my Kiti machines were powered up, along with my waterjet and a Tig welder. One of the Kiti's smoked and threw a bunch of errors. The other didn't flinch - both Fanuc controls. The waterjet was on but not running, seems ok. The Tig welder - made some really poopy welds. Doesn't smell burnt but we'll see once we get power back out there. We also lost a power supply on a Fanuc Robot....just powered it up and it blew....we thought it was a bad power supply until everything else happened... I hope your insurance company does you right, mine didn't. I was out of pocket about $25K. The insurance company sent in a "Forensic Engineer" who knew nothing about machine tools, he declared the motor would still rotate so no claim was paid. It did rotate, I admit that, but was only good for a conveyor or cement mixer since there was no way to control the speed. I hate the way insurance companies operate. 
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I hope your insurance company does you right, mine didn't. I was out of pocket about $25K. The insurance company sent in a "Forensic Engineer" who knew nothing about machine tools, he declared the motor would still rotate so no claim was paid. It did rotate, I admit that, but was only good for a conveyor or cement mixer since there was no way to control the speed. I hate the way insurance companies operate. Quoted:
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I feel your pain MBX, I had similar issues in a building I leased when I first started my shop. There was a pre-formed concrete plant behind me on the same branch line that would brown out then spike the entire area occasionally. One of my machines lost the spindle motor and controller, the Fanuc controlled machines survived miraculously but the Mitsubishi controls did not. Both of my Kiti machines were powered up, along with my waterjet and a Tig welder. One of the Kiti's smoked and threw a bunch of errors. The other didn't flinch - both Fanuc controls. The waterjet was on but not running, seems ok. The Tig welder - made some really poopy welds. Doesn't smell burnt but we'll see once we get power back out there. We also lost a power supply on a Fanuc Robot....just powered it up and it blew....we thought it was a bad power supply until everything else happened... I hope your insurance company does you right, mine didn't. I was out of pocket about $25K. The insurance company sent in a "Forensic Engineer" who knew nothing about machine tools, he declared the motor would still rotate so no claim was paid. It did rotate, I admit that, but was only good for a conveyor or cement mixer since there was no way to control the speed. I hate the way insurance companies operate. Man....I will implode if that happens....what a bunch of assholes! 
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I have 240vac 3ph incoming power - 3 wire delta. I've had some issues w/ our power company recently that has caused equipment damage, last month they lost a fuse down the road and it wasted parts in one of my cnc machines. I fixed it, and moved on... Today one of my Kitamura's threw a fault on Z axis, then a few seconds later 4 more power related errors and I smelled plastic smores.... Checked incoming voltage at the main - 240 phase to phase. But phase to ground is fucked up I think... 2 legs are 240 phase to ground, and one is zero volts.... Normally I thought it was supposed to be 120v phase to ground on each leg right? I am not 208 high leg delta. My other shop across the road has about 220vac incoming power, same 3 wire delta, and each leg is 120v phase to ground.... The fug is going on? Well if your normal power is 240 ,240,240 120 120 120 and you do not have a hi leg then you do not have corner grounded delta. You have what I call straight 240. In our area we do not see this but we have a lot of straight 480 also know as delta 480 or floating y 480. In any case the zero to ground indicates a grounded phase either in your system or in the light company system. A straight 480 or 240 system has its advantages and disadvantages but for drives and cnc machines most folks around here convert the old 480 systems to 277/480 and the straight 240 delta to 120 208 systems. One of the disadvantages of a straight 240 system is you can be running along with one or several grounds on phase a and then one day phase b develops a fault to ground and you have multiple blow ups at the same time. This is why grounded phase indicators are used to show you when this happens so you can orderly shut down the system and find the first fault. These faults can be anywhere on the system from the transformer on the pole to the last machine at the end of the shop. Trouble is when these type swings happen voltage to ground can spike really high and fuck up some drives power supplies etc. This is even more prevalent when there is a ground on one phase and a primary fuse on the transformer is blown. I have seen the voltage so high to ground that my fluke meter started beeping at me when I opened the switch gear and I have measured over 1200 volts to ground on a straight 480 system. But even 600 volts for a short time to ground on a floating 240 system will fry the shit out of many things. Changing to a 208 and preferably 480 system for all future equipment may seem expensive but that is my recommendation for growing machine shops Looking forward to update. |
| Phasing and phase loss gear/protection is expensive when designing a building. But when you have a unprotected phase loss/fault, well it is expensive. Had a switching motor in main gear fail, during a phase loss, double whammy on two 10 story wings of a hospital. And yes almost 7 digit expensive. OP, hope your insurance treats you well. You see now how troubleshooting 3 phase can be so much fun. Phase loss, neutral loss makes for a long night. |
| OP not sure what some people think is expensive but i built quite a bit of machinery with 3phase motors and rotation and single phasing was our main concern. relays can be had for around $150 give or take and wiring them in to the control circuits on a machine would cost minimal concerning the cost of smoked motors and controllers. id guess labor in time would be less then a our a machine, and depending on the electrician they could do 2 or 3 in a hr, but even at 1 a hr., its cheap insurance. |
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Quoted: Well if your normal power is 240 ,240,240 120 120 120 and you do not have a hi leg then you do not have corner grounded delta. You have what I call straight 240. In our area we do not see this but we have a lot of straight 480 also know as delta 480 or floating y 480. In any case the zero to ground indicates a grounded phase either in your system or in the light company system. A straight 480 or 240 system has its advantages and disadvantages but for drives and cnc machines most folks around here convert the old 480 systems to 277/480 and the straight 240 delta to 120 208 systems. One of the disadvantages of a straight 240 system is you can be running along with one or several grounds on phase a and then one day phase b develops a fault to ground and you have multiple blow ups at the same time. This is why grounded phase indicators are used to show you when this happens so you can orderly shut down the system and find the first fault. These faults can be anywhere on the system from the transformer on the pole to the last machine at the end of the shop. Trouble is when these type swings happen voltage to ground can spike really high and fuck up some drives power supplies etc. This is even more prevalent when there is a ground on one phase and a primary fuse on the transformer is blown. I have seen the voltage so high to ground that my fluke meter started beeping at me when I opened the switch gear and I have measured over 1200 volts to ground on a straight 480 system. But even 600 volts for a short time to ground on a floating 240 system will fry the shit out of many things. Changing to a 208 and preferably 480 system for all future equipment may seem expensive but that is my recommendation for growing machine shops Looking forward to update. Quoted: Quoted: I have 240vac 3ph incoming power - 3 wire delta. I've had some issues w/ our power company recently that has caused equipment damage, last month they lost a fuse down the road and it wasted parts in one of my cnc machines. I fixed it, and moved on... Today one of my Kitamura's threw a fault on Z axis, then a few seconds later 4 more power related errors and I smelled plastic smores.... Checked incoming voltage at the main - 240 phase to phase. But phase to ground is fucked up I think... 2 legs are 240 phase to ground, and one is zero volts.... Normally I thought it was supposed to be 120v phase to ground on each leg right? I am not 208 high leg delta. My other shop across the road has about 220vac incoming power, same 3 wire delta, and each leg is 120v phase to ground.... The fug is going on? Well if your normal power is 240 ,240,240 120 120 120 and you do not have a hi leg then you do not have corner grounded delta. You have what I call straight 240. In our area we do not see this but we have a lot of straight 480 also know as delta 480 or floating y 480. In any case the zero to ground indicates a grounded phase either in your system or in the light company system. A straight 480 or 240 system has its advantages and disadvantages but for drives and cnc machines most folks around here convert the old 480 systems to 277/480 and the straight 240 delta to 120 208 systems. One of the disadvantages of a straight 240 system is you can be running along with one or several grounds on phase a and then one day phase b develops a fault to ground and you have multiple blow ups at the same time. This is why grounded phase indicators are used to show you when this happens so you can orderly shut down the system and find the first fault. These faults can be anywhere on the system from the transformer on the pole to the last machine at the end of the shop. Trouble is when these type swings happen voltage to ground can spike really high and fuck up some drives power supplies etc. This is even more prevalent when there is a ground on one phase and a primary fuse on the transformer is blown. I have seen the voltage so high to ground that my fluke meter started beeping at me when I opened the switch gear and I have measured over 1200 volts to ground on a straight 480 system. But even 600 volts for a short time to ground on a floating 240 system will fry the shit out of many things. Changing to a 208 and preferably 480 system for all future equipment may seem expensive but that is my recommendation for growing machine shops Looking forward to update. If I'm understanding you correctly you're trying to imply he has a straight 240 Delta ungrounded system which I agree with you. An ungrounded system with 1 phase faulted to ground essentially becomes a half ass uncontrolled corner ground. When a second fault occurs to ground, you now have a phase-phase fault and this is what SHOULD trip a breaker or blow fuses. Regardless I agree with you about him needing fault detection Op you really need 2 things. Your equipment needs phase/voltage detection and your entire system needs ground fault detection. In fact, if you do not have a high leg, or a corner ground and you have an ungrounded Delta, it is code to have ground fault detection as you have no grounded conductor. |
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I have put these on one of my accounts that has very dirty power. They have saved countless motors. Highly recommend.
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He does not have a center tapped high leg how could he get readings of 120v? The only way to get 120v with a normal Delta system is with a center tap. A corner grounded Delta is different and with 240v Delta there also would be no 120. If I'm understanding you correctly you're trying to imply he has a straight 240 Delta ungrounded system which I agree with you. An ungrounded system with 1 phase faulted to ground essentially becomes a half ass uncontrolled corner ground. When a second fault occurs to ground, you now have a phase-phase fault and this is what SHOULD trip a breaker or blow fuses. Regardless I agree with you about him needing fault detection Op you really need 2 things. Your equipment needs phase/voltage detection and your entire system needs ground fault detection. In fact, if you do not have a high leg, or a corner ground and you have an ungrounded Delta, it is code to have ground fault detection as you have no grounded conductor. Quoted:
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I have 240vac 3ph incoming power - 3 wire delta. I've had some issues w/ our power company recently that has caused equipment damage, last month they lost a fuse down the road and it wasted parts in one of my cnc machines. I fixed it, and moved on... Today one of my Kitamura's threw a fault on Z axis, then a few seconds later 4 more power related errors and I smelled plastic smores.... Checked incoming voltage at the main - 240 phase to phase. But phase to ground is fucked up I think... 2 legs are 240 phase to ground, and one is zero volts.... Normally I thought it was supposed to be 120v phase to ground on each leg right? I am not 208 high leg delta. My other shop across the road has about 220vac incoming power, same 3 wire delta, and each leg is 120v phase to ground.... The fug is going on? Well if your normal power is 240 ,240,240 120 120 120 and you do not have a hi leg then you do not have corner grounded delta. You have what I call straight 240. In our area we do not see this but we have a lot of straight 480 also know as delta 480 or floating y 480. In any case the zero to ground indicates a grounded phase either in your system or in the light company system. A straight 480 or 240 system has its advantages and disadvantages but for drives and cnc machines most folks around here convert the old 480 systems to 277/480 and the straight 240 delta to 120 208 systems. One of the disadvantages of a straight 240 system is you can be running along with one or several grounds on phase a and then one day phase b develops a fault to ground and you have multiple blow ups at the same time. This is why grounded phase indicators are used to show you when this happens so you can orderly shut down the system and find the first fault. These faults can be anywhere on the system from the transformer on the pole to the last machine at the end of the shop. Trouble is when these type swings happen voltage to ground can spike really high and fuck up some drives power supplies etc. This is even more prevalent when there is a ground on one phase and a primary fuse on the transformer is blown. I have seen the voltage so high to ground that my fluke meter started beeping at me when I opened the switch gear and I have measured over 1200 volts to ground on a straight 480 system. But even 600 volts for a short time to ground on a floating 240 system will fry the shit out of many things. Changing to a 208 and preferably 480 system for all future equipment may seem expensive but that is my recommendation for growing machine shops Looking forward to update. Regardless I agree with you about him needing fault detection Op you really need 2 things. Your equipment needs phase/voltage detection and your entire system needs ground fault detection. In fact, if you do not have a high leg, or a corner ground and you have an ungrounded Delta, it is code to have ground fault detection as you have no grounded conductor. With a hi leg system you have two or three single phase transformers set up in a bank. The primary can be wye, grounded wye or delta depending on the voltage and number of pots. Two transformers would be an open delta and three transformers would be a closed delta or delta bank. An open delta giving about 58 percent of a three pot bank. in either case the voltage would read as follow 240 240 240 120 120 208 to ground. The center tap grounded pot would give the 120 to ground from either phase originating on the same winding. If you take these three pots and remove the center tap ground on one, then you will have 100 to 160 to ground floating mostly in this area {120} until one is grounded and at that point voltage two phases will jump to 240 or so and the other to zero to ground. This is the same with straight 480 but with straight 480 it is very rare to ground a center tap but doing so would create a hi leg of 416 voltage would read 480 480 480 - 240 240 416. It however is not uncommon to utilize single phase 480 with a grounded center tap giving 480 240 240. It can also be tied in a two pot bank open delta configuration. But is very rarely center tap grounded at least in Texas. Either 240 or 480 volt bank can be corner grounded but not with a center tap grounded. The only other way to have 120 120 120 to ground is with a wye wye bank with both wyes grounded. There is no hi leg and no chance of 240 to ground. Does this work out in your view and maybe things are different out side of my area. |
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He does not have a center tapped high leg how could he get readings of 120v? The only way to get 120v with a normal Delta system is with a center tap. A corner grounded Delta is different and with 240v Delta there also would be no 120. If I'm understanding you correctly you're trying to imply he has a straight 240 Delta ungrounded system which I agree with you. An ungrounded system with 1 phase faulted to ground essentially becomes a half ass uncontrolled corner ground. When a second fault occurs to ground, you now have a phase-phase fault and this is what SHOULD trip a breaker or blow fuses. Regardless I agree with you about him needing fault detection Op you really need 2 things. Your equipment needs phase/voltage detection and your entire system needs ground fault detection. In fact, if you do not have a high leg, or a corner ground and you have an ungrounded Delta, it is code to have ground fault detection as you have no grounded conductor. Quoted:
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I have 240vac 3ph incoming power - 3 wire delta. I've had some issues w/ our power company recently that has caused equipment damage, last month they lost a fuse down the road and it wasted parts in one of my cnc machines. I fixed it, and moved on... Today one of my Kitamura's threw a fault on Z axis, then a few seconds later 4 more power related errors and I smelled plastic smores.... Checked incoming voltage at the main - 240 phase to phase. But phase to ground is fucked up I think... 2 legs are 240 phase to ground, and one is zero volts.... Normally I thought it was supposed to be 120v phase to ground on each leg right? I am not 208 high leg delta. My other shop across the road has about 220vac incoming power, same 3 wire delta, and each leg is 120v phase to ground.... The fug is going on? Well if your normal power is 240 ,240,240 120 120 120 and you do not have a hi leg then you do not have corner grounded delta. You have what I call straight 240. In our area we do not see this but we have a lot of straight 480 also know as delta 480 or floating y 480. In any case the zero to ground indicates a grounded phase either in your system or in the light company system. A straight 480 or 240 system has its advantages and disadvantages but for drives and cnc machines most folks around here convert the old 480 systems to 277/480 and the straight 240 delta to 120 208 systems. One of the disadvantages of a straight 240 system is you can be running along with one or several grounds on phase a and then one day phase b develops a fault to ground and you have multiple blow ups at the same time. This is why grounded phase indicators are used to show you when this happens so you can orderly shut down the system and find the first fault. These faults can be anywhere on the system from the transformer on the pole to the last machine at the end of the shop. Trouble is when these type swings happen voltage to ground can spike really high and fuck up some drives power supplies etc. This is even more prevalent when there is a ground on one phase and a primary fuse on the transformer is blown. I have seen the voltage so high to ground that my fluke meter started beeping at me when I opened the switch gear and I have measured over 1200 volts to ground on a straight 480 system. But even 600 volts for a short time to ground on a floating 240 system will fry the shit out of many things. Changing to a 208 and preferably 480 system for all future equipment may seem expensive but that is my recommendation for growing machine shops Looking forward to update. Regardless I agree with you about him needing fault detection Op you really need 2 things. Your equipment needs phase/voltage detection and your entire system needs ground fault detection. In fact, if you do not have a high leg, or a corner ground and you have an ungrounded Delta, it is code to have ground fault detection as you have no grounded conductor. I should know better than to assume he has a grounded system.
An ungrounded delta system can operate fine with 1 phase grounded as the fault current is negligible and the phase voltages remains steady. The problem is when a second fault occurs and the line to line fault current is massive. Since that didn't happen, what damaged his equipment? A 173% rise of normal phase to ground voltage on the 2 ungrounded phases? OP. I hope the insurance co. covers you. I believe the power co. will claim it's your responsibility to provide protective equipment. |
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I should know better than to assume he has a grounded system.
An ungrounded delta system can operate fine with 1 phase grounded as the fault current is negligible and the phase voltages remains steady. The problem is when a second fault occurs and the line to line fault current is massive. Since that didn't happen, what damaged his equipment? A 173% rise of normal phase to ground voltage on the 2 ungrounded phases? OP. I hope the insurance co. covers you. I believe the power co. will claim it's your responsibility to provide protective equipment. Quoted:
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I have 240vac 3ph incoming power - 3 wire delta. I've had some issues w/ our power company recently that has caused equipment damage, last month they lost a fuse down the road and it wasted parts in one of my cnc machines. I fixed it, and moved on... Today one of my Kitamura's threw a fault on Z axis, then a few seconds later 4 more power related errors and I smelled plastic smores.... Checked incoming voltage at the main - 240 phase to phase. But phase to ground is fucked up I think... 2 legs are 240 phase to ground, and one is zero volts.... Normally I thought it was supposed to be 120v phase to ground on each leg right? I am not 208 high leg delta. My other shop across the road has about 220vac incoming power, same 3 wire delta, and each leg is 120v phase to ground.... The fug is going on? Well if your normal power is 240 ,240,240 120 120 120 and you do not have a hi leg then you do not have corner grounded delta. You have what I call straight 240. In our area we do not see this but we have a lot of straight 480 also know as delta 480 or floating y 480. In any case the zero to ground indicates a grounded phase either in your system or in the light company system. A straight 480 or 240 system has its advantages and disadvantages but for drives and cnc machines most folks around here convert the old 480 systems to 277/480 and the straight 240 delta to 120 208 systems. One of the disadvantages of a straight 240 system is you can be running along with one or several grounds on phase a and then one day phase b develops a fault to ground and you have multiple blow ups at the same time. This is why grounded phase indicators are used to show you when this happens so you can orderly shut down the system and find the first fault. These faults can be anywhere on the system from the transformer on the pole to the last machine at the end of the shop. Trouble is when these type swings happen voltage to ground can spike really high and fuck up some drives power supplies etc. This is even more prevalent when there is a ground on one phase and a primary fuse on the transformer is blown. I have seen the voltage so high to ground that my fluke meter started beeping at me when I opened the switch gear and I have measured over 1200 volts to ground on a straight 480 system. But even 600 volts for a short time to ground on a floating 240 system will fry the shit out of many things. Changing to a 208 and preferably 480 system for all future equipment may seem expensive but that is my recommendation for growing machine shops Looking forward to update. Regardless I agree with you about him needing fault detection Op you really need 2 things. Your equipment needs phase/voltage detection and your entire system needs ground fault detection. In fact, if you do not have a high leg, or a corner ground and you have an ungrounded Delta, it is code to have ground fault detection as you have no grounded conductor. I should know better than to assume he has a grounded system.
An ungrounded delta system can operate fine with 1 phase grounded as the fault current is negligible and the phase voltages remains steady. The problem is when a second fault occurs and the line to line fault current is massive. Since that didn't happen, what damaged his equipment? A 173% rise of normal phase to ground voltage on the 2 ungrounded phases? OP. I hope the insurance co. covers you. I believe the power co. will claim it's your responsibility to provide protective equipment. Exactly what this system is - an ungrounded delta and 1 phase grounded causing the issue. Luckily I am a Fanuc robot integrator, and I had all the parts on the shelf to fix my Kitamura - got it back online yesterday. Rebuilt the power supply and changed an IPM in the z-axis amp....rock and roll. Not sure I am going to win any battle w/ insurance or power co - so I just fixed the shit myself. Now for protection devices this week. |
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Exactly what this system is - an ungrounded delta and 1 phase grounded causing the issue. Luckily I am a Fanuc robot integrator, and I had all the parts on the shelf to fix my Kitamura - got it back online yesterday. Rebuilt the power supply and changed an IPM in the z-axis amp....rock and roll. Not sure I am going to win any battle w/ insurance or power co - so I just fixed the shit myself. Now for protection devices this week. Quoted:
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I have 240vac 3ph incoming power - 3 wire delta. I've had some issues w/ our power company recently that has caused equipment damage, last month they lost a fuse down the road and it wasted parts in one of my cnc machines. I fixed it, and moved on... Today one of my Kitamura's threw a fault on Z axis, then a few seconds later 4 more power related errors and I smelled plastic smores.... Checked incoming voltage at the main - 240 phase to phase. But phase to ground is fucked up I think... 2 legs are 240 phase to ground, and one is zero volts.... Normally I thought it was supposed to be 120v phase to ground on each leg right? I am not 208 high leg delta. My other shop across the road has about 220vac incoming power, same 3 wire delta, and each leg is 120v phase to ground.... The fug is going on? Well if your normal power is 240 ,240,240 120 120 120 and you do not have a hi leg then you do not have corner grounded delta. You have what I call straight 240. In our area we do not see this but we have a lot of straight 480 also know as delta 480 or floating y 480. In any case the zero to ground indicates a grounded phase either in your system or in the light company system. A straight 480 or 240 system has its advantages and disadvantages but for drives and cnc machines most folks around here convert the old 480 systems to 277/480 and the straight 240 delta to 120 208 systems. One of the disadvantages of a straight 240 system is you can be running along with one or several grounds on phase a and then one day phase b develops a fault to ground and you have multiple blow ups at the same time. This is why grounded phase indicators are used to show you when this happens so you can orderly shut down the system and find the first fault. These faults can be anywhere on the system from the transformer on the pole to the last machine at the end of the shop. Trouble is when these type swings happen voltage to ground can spike really high and fuck up some drives power supplies etc. This is even more prevalent when there is a ground on one phase and a primary fuse on the transformer is blown. I have seen the voltage so high to ground that my fluke meter started beeping at me when I opened the switch gear and I have measured over 1200 volts to ground on a straight 480 system. But even 600 volts for a short time to ground on a floating 240 system will fry the shit out of many things. Changing to a 208 and preferably 480 system for all future equipment may seem expensive but that is my recommendation for growing machine shops Looking forward to update. Regardless I agree with you about him needing fault detection Op you really need 2 things. Your equipment needs phase/voltage detection and your entire system needs ground fault detection. In fact, if you do not have a high leg, or a corner ground and you have an ungrounded Delta, it is code to have ground fault detection as you have no grounded conductor. I should know better than to assume he has a grounded system.
An ungrounded delta system can operate fine with 1 phase grounded as the fault current is negligible and the phase voltages remains steady. The problem is when a second fault occurs and the line to line fault current is massive. Since that didn't happen, what damaged his equipment? A 173% rise of normal phase to ground voltage on the 2 ungrounded phases? OP. I hope the insurance co. covers you. I believe the power co. will claim it's your responsibility to provide protective equipment. Exactly what this system is - an ungrounded delta and 1 phase grounded causing the issue. Luckily I am a Fanuc robot integrator, and I had all the parts on the shelf to fix my Kitamura - got it back online yesterday. Rebuilt the power supply and changed an IPM in the z-axis amp....rock and roll. Not sure I am going to win any battle w/ insurance or power co - so I just fixed the shit myself. Now for protection devices this week. Ungrounded delta was popular in industrial applications where loss of the power supply screwed up a process (aluminum extrusion, smelting, etc.). A grounded phase had no effect, as the 3 phase power was un-interrupted. I guess modern electronics have issues with 1 phase grounded. Glad you got back online. Maybe the power co. could update your WWII system. |