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Anonymous Poster

Three-Phase Current

09/30/2008 3:50 PM

If I have a 600A, 3P breaker, when would it trip? For example,

1) Does it trip when the sum of all 3 phase currents = 600A? or,

2) Does it trip when only one of the 3 phase currents = 600A?

Thank,

Hakeem Rabadobidibar
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wareagle
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#1

Re: Three-Phase Current

09/30/2008 5:41 PM

1) Does it trip when the sum of all 3 phase currents = 600A?

No. It will trip at some time when the load exceeds the breaker rating. If you have 601 amps the breaker would not trip. If you had 675 amps the breaker may trip but it might take hours for it to happen. There are curves that are associated with each breaker and these curves shows how much time it takes for different ampere increments.

2) Does it trip when only one of the 3 phase currents = 600A? It will trip if only on phase of the breaker is overloaded. Same as above.

Check the curves below.

http://ecatalog.squared.com/pubs/Circuit%20Protection/Molded%20Case%20Circuit%20Breakers/Thermal%20Magnetic%20Molded%20Case%20Circuit%20Breakers/FA-FC-FH/0600DB0105.pdf - sorry, link no longer available
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bob c
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#2
In reply to #1

Re: Three-Phase Current

09/30/2008 10:35 PM

Very well stated.

__________________
 Bob
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Anonymous Poster
#3

Re: Three-Phase Current

10/06/2008 12:04 PM

Good Question !!

Regards

PG
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