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Anonymous Poster

Generators and Transformers' Breaker Sizing

08/18/2010 3:57 PM

Hi,

Do we need to oversize the rating of the generator breaker each time we are sizing it? If so, why?

and does the cooling of the transformer (oil/forced air cooling) and the interlock system affect the sizing of its breaker?

Appreciate your prompt answer,

Thank you.
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wareagle
Guru
United States - Member - New Member

Join Date: Jun 2008
Location: Alabama
Posts: 1604
Good Answers: 63
#1

Re: Generators and Transformers' Breaker Sizing

08/18/2010 7:41 PM

What code are you using? NEC 115% generator 125% transformer.
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rockraiden
Power-User
Engineering Fields - Power Engineering - New Member

Join Date: Aug 2010
Posts: 111
Good Answers: 2
#2
In reply to #1

Re: Generators and Transformers' Breaker Sizing

08/18/2010 10:08 PM

you need to know your KAIC ratings too...over sizing is for future load growth...

__________________
 take care of your seconds and the minute will take care of itself..
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Anonymous Poster
#4
In reply to #2

Re: Generators and Transformers' Breaker Sizing

08/19/2010 12:55 AM

what is the KAIC?

Do you know if the cooling affects the sizing of the transformer's breaker?
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rockraiden
Power-User
Engineering Fields - Power Engineering - New Member

Join Date: Aug 2010
Posts: 111
Good Answers: 2
#5
In reply to #4

Re: Generators and Transformers' Breaker Sizing

08/19/2010 1:04 AM

its you kilo-ampere interrupting capacity...the breakers capacity to withstand huge amount of current in terms of thousands which is larger than your FLC(Full load Current)..happens during faults..subject your system to fault analysis..then look into cooling methods afterwards..

__________________
 take care of your seconds and the minute will take care of itself..
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Anonymous Poster
#3
In reply to #1

Re: Generators and Transformers' Breaker Sizing

08/19/2010 12:54 AM

Thank you. and what about the BS?

Do you know if the cooling affects the sizing of the transformer's breaker?
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rockraiden
Power-User
Engineering Fields - Power Engineering - New Member

Join Date: Aug 2010
Posts: 111
Good Answers: 2
#6
In reply to #3

Re: Generators and Transformers' Breaker Sizing

08/19/2010 1:07 AM

you simply use NEC/IEC standards..their similar and only using reciprocals with each other..and also varies with their DS employed..take note of the "must be's" and the "shall not's"...

__________________
 take care of your seconds and the minute will take care of itself..
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