Main-Neutral Interchange?
Main-Neutral Interchange?
(OP)
Hello,
Could you guys please explain to me what a main-neutral interchange procedure is for generator maintenance? I am currently working with some winders and they mentioned this type of work.
Thank You
Could you guys please explain to me what a main-neutral interchange procedure is for generator maintenance? I am currently working with some winders and they mentioned this type of work.
Thank You






RE: Main-Neutral Interchange?
Only thing I can think of is if you have multiple generators and a single point of grounding for all. There is usually procedure in place to isolate the generator completely from other system for maintenance. This includes isolating the neutral of the particular geneator in such way that other generators remains grounded. But then again I am guessing, something I should not.
RE: Main-Neutral Interchange?
I'm guessing also.
respectfully
RE: Main-Neutral Interchange?
That is interesting. Can you shed more light as to why is it done? I think that is what the OP is asking..
RE: Main-Neutral Interchange?
As you know, if one coil is reversed, the phase angles change from A-B 120, B-C 120, C-A 120 to A-C 60, C-b 60, B-A 240.
This would be corrected by interchanging the leads of the reverse connected coil. I have been wondering if there is a reason why all coils would be reversed.
Still guessing.
I hope one of the winding shop gurus drops in.
respectfully
RE: Main-Neutral Interchange?
Thanks. I was wondering why would you do it if there is nothing wrong with windings.
RE: Main-Neutral Interchange?
i am currently working an outage shift, and a generator is being rewound. the winders on this project told me that other companies employ this procedure to minimize maintenance costs. the winders explained to me when the main and neutrals are swithed the life of the generator can be extended. the time it takes to do this procedure is approx a 1/4 of the time to totally refurbish a generator. this is the first time i have seen the guts a huge generator, its been an experience to say the least! i imagined that there would be a group of people in lab coats doing the work, but i was surprised to see large rubber mallets, and crowbars being used. any of you guys know the advantages/disadvantes of doing this kind of procedure?
thanks for the replies!
FarmallFan
RE: Main-Neutral Interchange?
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Sometimes I only open my mouth to swap feet...
RE: Main-Neutral Interchange?
Workshop myths are long-lived and strange creatures.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Main-Neutral Interchange?
I think that modern insulation systems (Class F - epoxy)are less susceptible to voltage stress than the older systems (Class B - bitumen based), so the practice died out. Also, moving the connections may introduce mechanical stress on an older winding.
RE: Main-Neutral Interchange?
PLS for you.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Main-Neutral Interchange?
Also, wouldn't this practice require swapping phases as well? When doing that would the mechanical stresses felt by the coils be reversed? This idea of a main neutral interchange is new to me as well.
RE: Main-Neutral Interchange?
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Main-Neutral Interchange?
RE: Main-Neutral Interchange?
well i have found that this isnt really a myth. hoxton pretty much explained why this practice isnt used much. i also found out the generating company that has used method somewhat recently. all i need to do now is to find out who their outage supervisor was.
farmallfan
RE: Main-Neutral Interchange?
See if you can find out how big the unit was and how the exchange was achieved, particularly:
- Whether the line cubicle became the neutral and the neutral cubicle the line;
- Whether the endwinding connections were re-routed internally (and was the bracing re-calculated for fault withstand);
I asked this question of one of our outage supervisors and he looked at me very strangely. I tried to explain further - with this thread - and he indicated that he thought I was mad. Maybe it is a practice which has never been used in the UK?----------------------------------
Sometimes I only open my mouth to swap feet...
RE: Main-Neutral Interchange?
If it is a large generator (or motor), line and neutral may be on opposite sides of the machine, so you have to re-lay or replace the external cabling (or bus-ducts on very large machines). If you re-connect internally, then you are interfering with existing connections which have to be re-made, and re-braced, thereby putting mechanical stress on the insulation.
First Law of motorcycle maintenance: things that aren't broken don't need mending!
RE: Main-Neutral Interchange?