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Posted by Bubba on August 29, 2007, 10:25 pm
>Paul C wrote:
>> 460 volts
>> units are from this century
>> something in 250 amp switch L3 suddenly gets real hot. checked unit
>> weeks ago ok temp. now temp is over 250 degrees on L3. shut down unit
>> from breakers.
>>
>
>You've GOTTA be shitting me....
>
>You're working a 250 Amp 480 Volt circuit and you're NOT an electrician.
>
>... and if YOU ARE.... how about some more info:
>
>Is the circuit loaded with a VFD or soft-start? Did you isolate those
>devices and megger everything for ground fault on L3?
>
>A 250A circuit should be at least 4/0 THHN rated for 90 (c). 90 (c) is
>194 (f). If you or the circuit protection allowed the wiring to get to
>250 (f).. it's toast. Replace it FIRST.
English Jake.......English! hehehe
No, actually i understood everything and THAT is what really scares
the hell outta me! :-)
Bubba
>
>After you've checked for ground faults, make certain all components have
>equal resistance across the phases. Also make sure ALL fusing or other
>circuit protection is adequately rated... and NOT over. People love to
>over-fuse stuff and then make themselves bigger problems later.
>
>I've worked on some Mammoth units (electrical-wise). They are still
>around and make pretty decent custom one-offs for big buildings,
>stadiums and the like. They're a part of another outfit that makes a
>whole range of custom equipment.
>
>Jake
>
>
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