Previous in Forum: Metal Halide Lights   Next in Forum: Electrical
Close

Comments Format:






Change Mode
Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







Add Vote
8 comments
Rate this Comments: Nested
saraswata1981
Associate

Join Date: Nov 2009
Posts: 27

Making Capacity of Breaker

04/08/2015 1:47 AM

If we go by the book, the making capacity of breaker shall be min 2.5 times of breaking capacity whereas for 50KA short circuit current making capacity of breakert is tested on 105 KA. It should be far more than 105 KA if we go by the text. Please help .
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".
Crabtree
Guru

Join Date: Jul 2007
Location: Commissariat de Police, Nouvions, occupied France, 1942.
Posts: 2599
Good Answers: 77
#1

Re: making capacity of breaker

04/08/2015 2:26 AM

Help with what, Mildred?

__________________
 Good moaning!
Register to Reply Score 1 for Off Topic
lyn
Guru

Join Date: Oct 2008
Posts: 42377
Good Answers: 1691
#2

Re: making capacity of breaker

04/08/2015 3:02 AM

You are beyond help.

Just go by the book.
Register to Reply
3
kvsridhar
Guru
India - Member - New Member

Join Date: Sep 2009
Location: Temporarily at Ashburn, VA
Posts: 2744
Good Answers: 164
#3

Re: Making Capacity of Breaker

04/08/2015 7:41 AM

As the experts have said, go by the book. However, you should be aware of two things :

(a) Making current is a peak value, while breaking current is a RMS value. So you have a factor of 1.414 already on 50kA, making it 70kA. Then there is asymmetry for the first few cycles depending on the various parameters, making it 105kA Peak.

(b) Not all 50kA breakers are capable of making and LATCHING on when closing on to a 105kA peak fault. It is not alwys necessary. Google "Making current release" to know more.

__________________
 Nothing worthwhile can ever be taught, it can only be learnt.
Register to Reply Good Answer (Score 3)
No more Good Answers.
jack of all trades
Guru
New Zealand - Member - Kiwi Popular Science - Weaponology - New Member Engineering Fields - Power Engineering - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: Auckland, New Zealand
Posts: 8778
Good Answers: 376
#4

Re: Making Capacity of Breaker

04/08/2015 3:38 PM

If we go by the book, the making capacity of breaker shall be min 2.5 times of breaking capacity

For what, capacitive loads?

Do you realise the ratings and short circuit test durations of circuit breakers vary, also with load?

Have you checked circuit breaker manufacture data sheets and applicable standards which override whatever 'rule of thumb' you have found in a book?

Please help .

Your past posts indicate your are working in the Indian power industry and have been for some time. Try performing your own basic research first, switchgear supplier literature is a good start and is free.

__________________
 jack of all trades
Register to Reply
Crabtree
Guru

Join Date: Jul 2007
Location: Commissariat de Police, Nouvions, occupied France, 1942.
Posts: 2599
Good Answers: 77
#5

Re: Making Capacity of Breaker

04/09/2015 5:12 AM

Which book are you working to? Why do you think it is wrong?

__________________
 Good moaning!
Register to Reply
Anonymous Poster #1
#7
In reply to #5

Re: Making Capacity of Breaker

04/10/2015 2:00 AM

@Crabtree
Please give answer or dont post.. Few members like you had downgrading this beautifull webpage...Are you trying utmost to kill this forum for ever??? everybody is getting disturbed now...
Register to Reply
pnaban
Guru

Join Date: Jun 2010
Location: srilanka
Posts: 2725
Good Answers: 5
#6

Re: Making Capacity of Breaker

04/10/2015 1:30 AM

When you make a circuit(reclosing for example)you may not know whether fault is cleared or any short circuit exists.therefore as a precautionary measure making capacity should be higher.

__________________
 pnaban
Register to Reply
Rajesh52
Associate

Join Date: Jun 2019
Posts: 50
Good Answers: 1
#8

Re: Making Capacity of Breaker

06/26/2019 9:04 AM

The making current capacity of the breaker should be 2.55 times of its breaking current capacity. if the breaker is closed at fault, the current will be almost two times of the symmetrical breaking capacity of the breaker because of DC current for one to two cycles.

Read More:https://sdvelectrical.blogspot.com/2019/06/why-making-current-of-circuit-breaker-is-more-than-breaking-current.html
Register to Reply
Register to Reply 8 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".
Copy to Clipboard

Users who posted comments:

Anonymous Poster (1); Crabtree (2); jack of all trades (1); kvsridhar (1); lyn (1); pnaban (1); Rajesh52 (1)

Previous in Forum: Metal Halide Lights   Next in Forum: Electrical

Advertisement

Got Something to Say?
Ask a Question
Start a Discussion

Search this Forum
Electrical Engineering:
Go

CR4 Sections
Aerospace
BioMech & BioMed
Chemical & Material Science
Civil Engineering
Communications & Electronics
Education and Engineering Careers
Electrical Engineering
General Discussion
Instrumentation
Manufacturing
Mechanical Engineering
New Technologies & Research
Software & Programming
Sustainable Engineering
Transportation

Site Directories
Forum Directory
Blog Directory
User Group Directory
RSS Feeds

CR4 Rules of Conduct
CR4 FAQ
Site Glossary

Who's Online (51 right now)
Show Members
Advertisement