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Joined: Jul 2002
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With a recent factory upgrade, I had the un-enviable task of throwing the Main Isolator, back into service, and got the handle stuck half way, I heard and saw welding of the contacts inside the Isolator (1000A@400V). How would you go about opening or closing a High current Isolator, have I got it all wrong?.
[This message has been edited by Trumpy (edited 11-26-2002).]
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Joined: Apr 2001
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What I have allways done is;
Remove as much load as possible.
When you go to throw the switch, commit to the action and close it fast and hard.
If you have a chance to examine the switch de-energised always take the opportunity to do it. Often these switches haven't been moved in years and then we expect them to operate like new. A little lubrication helps a bunch.
GJ
GJ
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An "ACB" is mentioned, and on the North-American continent, there are 3 types of breaker construction in that range—air-{frame}, insulated-case and molded-case. In my experience, air-frame breakers are generally "rackable," meaning they can be mechanically exercised/checked to operate in a test position—unenergized.
After the fact, I would want to determine if the fault duty was too high, and if the breaker manufacturer provided any maintenance instructions. Sounds like you were able to sidestep a potentially serious accident. Because of the breaker misoperation, it integral ground-fault protection may have been useless.
In the US, NFPA 70E {Electrical Safety Requirements for Employee Workplaces} calls for evaluation of arc-blast hazards, and appropriate personal protective equipment.
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Joined: Jul 2002
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Sorry, the part that said ACB, should have read Isolator, this is now amended. Have since locked off the supply and cleaned the contacts and lubed the operating mechanism, works like a charm, now. But this was an old metal-clad unit(the norm in Industrial installations, over here).
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Joined: Apr 2002
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In the US, NEMA {nema.org} has somewhat applicable standards that are on line—ICS2.3-1995 Annex A ‘Maintenance of Motor Controllers After a Fault Condition.’
These are basically common sense, but seem worth reviewing. Handy for establishing that endless “paper trail.”
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