Forum Discussion
32 Replies
Salvo wrote:
You have a reading comprehension problem. I said the resistance between the lug edge and the stud is orders of magnitude greater than the resistance between the compressed stack of lugs. So yes, some fraction of current will flow from stud to lug.
When you consider the stud has V-shaped threads, there's very little contact between the stud and a small part of the inside edge of the lug.
You're making a mountain out of a molehill.OnaQuest wrote:
Salvo wrote:
Who pushed your button? There's a good chance the wire lugs make no contact with the stud. Current flows through the stack of lugs. The resistance between lug and stud is orders of magnitude greater than the resistance between lugs. There is no compressive force between lug and stud, that's why this resistance is high.OnaQuest wrote:
I don't need to read it again. I agree, the stud in the first case IS NOT DESIGNED to carry the current, but if you think there is no current flow through the stud, especially if there is any resistance in that tall stack of terminals, you're wrong.
No one ever said, or even implied, that the edge of any terminal against the stud was a reliable current path. Some of you folks are just too narrow minded to consider the facts. Current can very easily pass (and would probably be impossible to stop) through the terminal contact with the nut, through the tightened threads, and on down the stud.
This is a fact, and is expected and depended upon in many grounding lug situations for otherwise insulated chassis configurations. Accept it, and get over yourself.
And you, sir, are missing my point entirely. When one tightens the top nut (down against the terminal flat surface), it makes contact via compression. That creates a solid path for current to flow into the nut, through the considerable thread surface area of nut/stud connection, thus into and through the stud, if required. There's no reason why this phenomenon can't, or shouldn't, be utilized when necessary. The resultant path is at least as reliable as that stack of 7 or 8 lugs (or even the recommended 4) in the examples.
I'm not sure where you got the idea that my described connection was dependent on thread and/or terminal edge contact. Possibly a reading comprehension problem?
Until current only flows where and when some of you guys seem to think, I would suggest that you keep one hand in your pocket at all times.- I agree Salvo. The edge of the lug (terminal) may not make a major contact with the stud. The lug hole is sized for the size of the stud before the threads are cut. Cutting the threads reduces the size of the stud slightly.
Corrosion can also build up between a lug (terminal) and the stud. This is when it is good to use electrical grease to reduce the rate of corrosion.
Of course, what happens when someone uses a 3/8 inch ring terminal on a 1/4 stud? Even less contact! - You have a reading comprehension problem. I said the resistance between the lug edge and the stud is orders of magnitude greater than the resistance between the compressed stack of lugs. So yes, some fraction of current will flow from stud to lug.
When you consider the stud has V-shaped threads, there's very little contact between the stud and a small part of the inside edge of the lug.
You're making a mountain out of a molehill.OnaQuest wrote:
Salvo wrote:
Who pushed your button? There's a good chance the wire lugs make no contact with the stud. Current flows through the stack of lugs. The resistance between lug and stud is orders of magnitude greater than the resistance between lugs. There is no compressive force between lug and stud, that's why this resistance is high.OnaQuest wrote:
I don't need to read it again. I agree, the stud in the first case IS NOT DESIGNED to carry the current, but if you think there is no current flow through the stud, especially if there is any resistance in that tall stack of terminals, you're wrong.
No one ever said, or even implied, that the edge of any terminal against the stud was a reliable current path. Some of you folks are just too narrow minded to consider the facts. Current can very easily pass (and would probably be impossible to stop) through the terminal contact with the nut, through the tightened threads, and on down the stud.
This is a fact, and is expected and depended upon in many grounding lug situations for otherwise insulated chassis configurations. Accept it, and get over yourself. Salvo wrote:
Who pushed your button? There's a good chance the wire lugs make no contact with the stud. Current flows through the stack of lugs. The resistance between lug and stud is orders of magnitude greater than the resistance between lugs. There is no compressive force between lug and stud, that's why this resistance is high.OnaQuest wrote:
I don't need to read it again. I agree, the stud in the first case IS NOT DESIGNED to carry the current, but if you think there is no current flow through the stud, especially if there is any resistance in that tall stack of terminals, you're wrong.
No one ever said, or even implied, that the edge of any terminal against the stud was a reliable current path. Some of you folks are just too narrow minded to consider the facts. Current can very easily pass (and would probably be impossible to stop) through the terminal contact with the nut, through the tightened threads, and on down the stud.
This is a fact, and is expected and depended upon in many grounding lug situations for otherwise insulated chassis configurations. Accept it, and get over yourself.- Who pushed your button? There's a good chance the wire lugs make no contact with the stud. Current flows through the stack of lugs. The resistance between lug and stud is orders of magnitude greater than the resistance between lugs. There is no compressive force between lug and stud, that's why this resistance is high.
OnaQuest wrote:
I don't need to read it again. I agree, the stud in the first case IS NOT DESIGNED to carry the current, but if you think there is no current flow through the stud, especially if there is any resistance in that tall stack of terminals, you're wrong. - That is exactly what I am saying. The load or in the case of diagram on page 8, ground passes through the star washer and the face of the nuts.
- I think you will find this interesting and controversial. Look at the drawing and text on page 8:
http://literature.rockwellautomation.com/idc/groups/literature/documents/in/1770-in041_-en-p.pdf - I do not understand why some cannot follow that the surface area (face) of the terminal and nut or bolt is where the contact is made. and not the edge of the terminal. If you rely on the edge of the terminal, there would not be sufficient area to carry the load.
OnaQuest wrote:
I don't need to read it again. I agree, the stud in the first case IS NOT DESIGNED to carry the current, but if you think there is no current flow through the stud, especially if there is any resistance in that tall stack of terminals, you're wrong.
That's what I said- it is not meant (IOW- designed) to carry current. That was in response to wondering if 4 terminals /nut/terminals/nut would be acceptable. My answer- no, for reasons I gave.
I'm sure they do carry current, I'm also sure that only happens when something is not right.Chris Bryant wrote:
Geez- I really didn't think this was much of a secret- it's pretty well documented. Sorry I brought it up, just trying to educate- I regret that now.
No need to be sorry. I just took exception to your statement that using the stud threads to help carry the current would introduce many problems. As you stated above, you would have to get creative to design a stud termination (plastic insulated nuts, etc.) that didn't allow or take advantage of it's ability to conduct current. I assure you, that in 50+ years of electrical engineering, I've seen more than a few instances where conduction of current through a threaded bolt (stud) was depended on. Is it good design? NO, but that's why we have nuts with attached star washers and other means of penetrating the surface of the terminal ring, rather than just depending on compression alone.
I'm done playing. It's been fun.
