54067323 (banned)
join:2012-09-25
Tuscaloosa, AL |
to whizkid3
Re: [Electrical] 230V 50A GFCIsaid by whizkid3:I believe the secondary of the transformer is purposefully not grounded. Otherwise, one would have to isolate the materials one is welding from ground, which is unfeasible. I have three welders and on all three of them the secondary is floating for just that reason. As such a GFI serves no purpose. |
|
|
| |
said by 54067323:said by whizkid3:I believe the secondary of the transformer is purposefully not grounded. Otherwise, one would have to isolate the materials one is welding from ground, which is unfeasible. I have three welders and on all three of them the secondary is floating for just that reason. As such a GFI serves no purpose. it prevents THIS. » nasdonline.org/document/ ··· ker.htmlAlthough GFCIs are not normally used with welders in farm settings, a GFCI would have detected if there were a current leakage in the electrical cable between the welder and the electrical outlet. The electrical circuit would have been interrupted and the welder would have turned off, indicating to the victim that the power to the welder was "unsafe". |
|
| |
The power supply to the welder is not what electrocuted him. He was on the secondary welding circuit. |
|
|
54067323 (banned)
join:2012-09-25
Tuscaloosa, AL |
to iknow_t
said by iknow_t:Although GFCIs are not normally used with welders in farm settings, a GFCI would have detected if there were a current leakage in the electrical cable between the welder and the electrical outlet. The electrical circuit would have been interrupted and the welder would have turned off, indicating to the victim that the power to the welder was "unsafe". Totally incorrect, the operator was electrocuted, in part, by allowing the isolated secondary of the welder to become grounded. “To allow the welding leads to reach the location of the feed bunker wagon, the victim connected two sets of welding cables and placed the un-insulated cable splices on bare dirt.” This “un-intentional ground” would have not been detected by a GFCI on the primary side of the welder as the primary of that welder is isolated from the secondary, therefore having such a device (GFCI) would have not made a difference in the outcome. |
|
| |
to Jack_in_VA
said by Jack_in_VA:The power supply to the welder is not what electrocuted him. He was on the secondary welding circuit. yes, but the welder was in great disrepair, and could have had a leakage between the primary and secondary windings. the cord or outlet could have had a bad ground. none of the components on the primary was safe.. notice that his helper got a shock when he touched the body.. |
|
| |
to 54067323
said by 54067323:said by iknow_t:Although GFCIs are not normally used with welders in farm settings, a GFCI would have detected if there were a current leakage in the electrical cable between the welder and the electrical outlet. The electrical circuit would have been interrupted and the welder would have turned off, indicating to the victim that the power to the welder was "unsafe". Totally incorrect, the operator was electrocuted, in part, by allowing the isolated secondary of the welder to become grounded. “To allow the welding leads to reach the location of the feed bunker wagon, the victim connected two sets of welding cables and placed the un-insulated cable splices on bare dirt.” This “un-intentional ground” would have not been detected by a GFCI on the primary side of the welder as the primary of that welder is isolated from the secondary, therefore having such a device (GFCI) would have not made a difference in the outcome. We used to hang 3 or 4 welders on a 480 volt circuit in the plant. Welders should know the basics of personal protective and safety measures when using a welder. |
|
 shdesignsPowered By Infinite Improbabilty Drive
Premium Member
join:2000-12-01
Stone Mountain, GA
ARRIS SB6121
|
to iknow_t
said by iknow_t:yes, but the welder was in great disrepair, and could have had a leakage between the primary and secondary windings. the cord or outlet could have had a bad ground. none of the components on the primary was safe.. notice that his helper got a shock when he touched the body.. Welders like he used operate on 90VAC, plenty enough to shock someone. A GFCI would not have helped in this case. |
|
54067323 (banned)
join:2012-09-25
Tuscaloosa, AL |
to iknow_t
said by iknow_t:yes, but the welder was in great disrepair, and could have had a leakage between the primary and secondary windings. the cord or outlet could have had a bad ground. Makes no difference and compared to many welders I have seen in the field I would like you to explain how you determined that one was in great disrepair??? Your grasping at straws now... notice that his helper got a shock when he touched the body.. You need to understand how the connection in the dirt caused that to happen, not the welder, or a lack of a GFCI. And instead of arguing minutia (GFCI) understand the output of a buzz box welder such as that one is around 70+ volts AC, depending on the amperage setting and that is more than enough to electrocute a person who is both in contact with ground and the stinger. |
|
| 54067323 |
to Jack_in_VA
said by Jack_in_VA:Welders should know the basics of personal protective and safety measures when using a welder. Welders for the most part do, farmers who knows, on the other hand when it’s pissing rain and ones boots, clothing, gloves and stinger is soaked, a welder (by profession) will put up with a zap or two while finishing up hard surfacing that last few inches of a front end loaders shear blade and then go home. |
|
lutful... of ideas
Premium Member
join:2005-06-16
Ottawa, ON
2 edits |
to shdesigns
said by shdesigns:Welders like he used operate on 90VAC, plenty enough to shock someone. A GFCI would not have helped in this case. I came across your DIY welder website and some of your other electrical projects. I think it is possible to add protection on the welder side using Rogowski coils around the electrode and return conductors. Detect significant difference in current and quickly shut off the welder's power supply? *** Anyway, my original suggestion was for the incoming AC path to a welder which can pose a serious shock hazard under many different fault scenarios. A properly rated RCD on the mains side may not be "required" by code, but does not mean they will provide no benefit. I consistently use the proper technical term "residual current device" or RCD mainly because of the rampant ignorance created by limitations of 120V residential GFCI devices used in the US. |
|
54067323 (banned)
join:2012-09-25
Tuscaloosa, AL
1 edit |
54067323 (banned)
Member
2013-Nov-3 12:00 pm
said by lutful:I think it is possible to add protection on the welder side using Rogowski coils around the electrode and return conductors. Detect significant difference in current and quickly shut off the welder's power supply? That would not work as even if the path of current was through the operator, the feed and return current would be the same, what you fail to understand is with a transformer that has an isolated secondary there is no path to ground which is how a GFCI device detects a ground fault, hence the term "Ground Fault" Circuit Interrupter. A GFCI works by measuring the amount of current on the hot and compares it to the current on the neutral and as long as they are equal no trip, however if the hot current is MORE then the neutral that indicates a “ground fault” which trips the GFCI. I consistently use the proper technical term "residual current device" or RCD mainly because of the rampant ignorance created by limitations of 120V residential GFCI devices used in the US. I doubt you will find any ignorance of the workings or proper application of a GFCI device by those actually versed in electrical contracting/engineering in this forum. |
|
lutful... of ideas
Premium Member
join:2005-06-16
Ottawa, ON
1 edit |
to shdesigns
said by shdesigns:Welders like he used operate on 90VAC, plenty enough to shock someone. I am asking a sincere question ... could a barefoot person touch the 90VAC electrode with bare hand on a rainy day? Assume he was working on a large metal object sitting on mud. |
|
54067323 (banned)
join:2012-09-25
Tuscaloosa, AL
1 edit |
54067323 (banned)
Member
2013-Nov-4 6:19 am
said by lutful:I am asking a sincere question ... could a barefoot person touch the 90VAC electrode with bare hand on a rainy day? Yes and not get shocked either. The reason being, like a bird sitting on a 7.62 Kv power line, no return path no shock. Assume he was working on a large metal object sitting on mud. Assumed, now what?? |
|
54067323
1 edit |
to lutful
Dupe deleted. |
|
1 edit |
to lutful
said by lutful:said by shdesigns:Welders like he used operate on 90VAC, plenty enough to shock someone. A GFCI would not have helped in this case. I came across your DIY welder website and some of your other electrical projects. I think it is possible to add protection on the welder side using Rogowski coils around the electrode and return conductors. Detect significant difference in current and quickly shut off the welder's power supply? *** Anyway, my original suggestion was for the incoming AC path to a welder which can pose a serious shock hazard under many different fault scenarios. A properly rated RCD on the mains side may not be "required" by code, but does not mean they will provide no benefit. I consistently use the proper technical term "residual current device" or RCD mainly because of the rampant ignorance created by limitations of 120V residential GFCI devices used in the US. welders are not supposed to be above 80 volts to reduce the shock hazard. also, the simple solution to prevent shocks is to put a metal band on one arm or leg, and connect a wire to it going to a control board that will shut the power down if it senses a voltage between the welding person and the ground clamp. there's not normally a voltage there. |
|
54067323 (banned)
join:2012-09-25
Tuscaloosa, AL
4 edits |
54067323 (banned)
Member
2013-Nov-6 2:59 pm
said by iknow_t:the simple solution to prevent shocks is to put a metal band on one arm or leg, and connect a wire to it going to a control board that will shut the power down if it senses a voltage between the welding person and the ground clamp. there's not normally a voltage there. The primary problem with that and other suggestions is they are semi-solutions to nonexistent problems, a person operating a welder, following proper safety practices and using proper PPE is not subject to being electrocuted to begin with. The second impractical part of these "solutions" is they fail to take into account the variables in welder operations, such as use of multiple welders in high rise and heavy construction situations or under water welding operations and in many cases will actually introduce additional shock hazards in the process by de-isolating the secondary or providing multiple return paths for leakage current. And then there are human factors such as failing to maintain equipment, the bypassing of safety devices, leaving un-insulated connections on the ground or welding in ones bare feet and no matter how well designed a system is, Darwin will win every time over technology when it comes to dealing with stuck on stupid end users. BTW welding in bare feet can only be classified as a special kind of stupid, right up there with not using a hood or gloves and it's not just the shock hazard doing so can create, but the UV and slag burns one will suffer on exposed skin in doing so. Heck I have had slag burn through a work boot and get me, I could not even imagine doing even a quick patch weld without my boots, long sleeves, long pants and gloves on. Lastly there is the cost versus benefit factor, earlier in the thread it was suggested that the installation of a Littelfuse GFCI could have prevented the electrocution of a person operating a welder, one problem with that is the GFCI recommended costs around four times the price of the $300 poorly maintained and mis-wired welder being used, ideas like that are simply not practical solutions, nor will they ever see the light of day in real world situations. |
|
lutful... of ideas
Premium Member
join:2005-06-16
Ottawa, ON |
to iknow_t
said by iknow_t:welders are not supposed to be above 80 volts to reduce the shock hazard. The fatal shock hazards actually come from various fault scenarios such as: - short between 240V primary and 80/90V secondary - short from 240V L or N conductor to metal case - short from electrode or return conductor to metal case said by iknow_t:metal band on one arm or leg ... If the person contacts line voltage with some other parts of his body, this metal band could even cause death by providing a return path. Anyway, our skin/body resistance is relatively high for this scheme to work. Anyway, many industrial welding setups are using residual current method already to prevent deaths. I upload a few relevant snippets. |
|
54067323 (banned)
join:2012-09-25
Tuscaloosa, AL
3 edits |
54067323 (banned)
Member
2013-Nov-7 6:54 am
said by lutful:The fatal shock hazards actually come from various fault scenarios such as:- short between 240V primary and 80/90V secondary Cannot happen as the windings are on two separate bobbins with a common steel core, if the primary shorted out it would at worst connect to the core shorting to ground and tripping the upstream protective device. - short from 240V L or N conductor to metal case Now a short from L to the case will also trip the protective device, no GFCI needed and you need to understand to understand portable 240 volt welders only have three prong cords consisting of two hots (L) and a ground, as such there is NO neutral conductor to short to the case. Note the cord (9) on the parts diagram of a standard Lincoln AC-225-GLM 225 amp stick welder, there are only three wires, not four precluding the use of a neutral. 
Anyway, many industrial welding setups are using residual current method already to prevent deaths. I upload a few relevant snippets. And they are not relevant to the OP's question, nor the protection spinoff from it. Also again you need to understand the error in you mis-interpertation/mis-application of the code that industrial welders are a different beast compared to cord connected "portable welders" such as the OP is referring to. One is part of a larger machine commonly utilizing robots and the other is used by welders to perform their day-to-day work, they are two different worlds with two different requirements. |
|
