It is currently Wed May 27, 2020 6:36 pm



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: IEEE 1584 - 2018.....Last Equation in Standard
PostPosted: Thu May 07, 2020 2:28 pm 

Joined: Tue Aug 26, 2008 7:15 am
Posts: 6
I apologize in advance if this has been asked, but can someone make heads or tails out of the very last equation in the Standard (also on the last page)? From what I can tell, it doesn't appear mathematically correct as it seems to be missing a term. Perhaps it's just my copy, but I don't think so. Any clarification would be greatly appreciated!

Thanks in advance.

Ernie Bowles
EB Consulting


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: IEEE 1584 - 2018.....Last Equation in Standard
PostPosted: Mon May 11, 2020 5:13 pm 
Sparks Level
User avatar

Joined: Wed Jun 10, 2009 5:00 pm
Posts: 262
Location: Toronto
ebowles wrote:
I apologize in advance if this has been asked, but can someone make heads or tails out of the very last equation in the Standard (also on the last page)? From what I can tell, it doesn't appear mathematically correct as it seems to be missing a term. Perhaps it's just my copy, but I don't think so. Any clarification would be greatly appreciated!

Thanks in advance.

Ernie Bowles
EB Consulting


could you please let me know what equation you are questioning exactly?

_________________
Michael Furtak, C.E.T.
http://arcadvisor.com


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: IEEE 1584 - 2018.....Last Equation in Standard
PostPosted: Mon May 18, 2020 8:51 am 

Joined: Tue Aug 26, 2008 7:15 am
Posts: 6
Annex I - Development of Special Model for Circuit Breakers

Equation I.4, solving for Ibf.....should there not be a term after "log"? All I see is an exponent that I can't really read.

Thanks!


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: IEEE 1584 - 2018.....Last Equation in Standard
PostPosted: Tue May 19, 2020 10:00 am 
Plasma Level
User avatar

Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1479
Location: Scottsdale, Arizona
ebowles wrote:
Annex I - Development of Special Model for Circuit Breakers

Equation I.4, solving for Ibf.....should there not be a term after "log"? All I see is an exponent that I can't really read.

Thanks!


I believe it may be a typo (unofficially - I have not confirmed with the committee yet)

This is verbatim (almost) from the 2002 Edition of IEEE 1584 page 62. In that edition the equation was:

Ibf = I1 = 10^(log * I1)

It looks like in the 2018 edition a superscript was lost. "log" should be part of the superscript. log * I1 not log^I1

Good catch - thanks. I will report back once I confirm.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: IEEE 1584 - 2018.....Last Equation in Standard
PostPosted: Tue May 19, 2020 10:51 am 

Joined: Tue Aug 26, 2008 7:15 am
Posts: 6
Thank you Jim.....I'm glad I was able to make a contribution :)

One other question while you're on topic.....the equation itself, to me, doesn't make sense......the term I1 is being solved for as a function of itself.....it's like having an equation such as X = 4X instead of X = 4Y......in the first equation, if X = 2, then it can't also be equal to 8.

I'll look forward to your response, and thanks!

Ernie Bowles
EB Consulting


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: IEEE 1584 - 2018.....Last Equation in Standard
PostPosted: Tue May 19, 2020 2:27 pm 
Plasma Level
User avatar

Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1479
Location: Scottsdale, Arizona
ebowles wrote:
Thank you Jim.....I'm glad I was able to make a contribution :)

One other question while you're on topic.....the equation itself, to me, doesn't make sense......the term I1 is being solved for as a function of itself.....it's like having an equation such as X = 4X instead of X = 4Y......in the first equation, if X = 2, then it can't also be equal to 8.

I'll look forward to your response, and thanks!

Ernie Bowles
EB Consulting


After considerable thought my conclusion is - you might be the first to have actually read Annex I :D

This material is a carry over from the 2002 standard and the information was from a specific manufacturer and from what I understand was based on that manufacturer's devices. I believe it was an attempt to simplify what was known in 2002 and of course we know orders of magnitude more now.

Specific to your question: I agree equation I.4 seems like something is not correct. It is the same equation from 2002. I don't know if the "dot" should be a different operator such as + or what happened. I believe the people behind the original work are no longer involved.

The simple (?) solution is ignore it and focus on the 2018 equations.

Great question Ernie, it certainly got me scratching my head! (which now hurts)

btw, this is my personal view and can't be taken as an official position of IEEE or any other standards organization.

Thanks

- Jim


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: IEEE 1584 - 2018.....Last Equation in Standard
PostPosted: Wed May 20, 2020 7:34 am 
Sparks Level
User avatar

Joined: Wed Jun 10, 2009 5:00 pm
Posts: 262
Location: Toronto
ebowles wrote:
Annex I - Development of Special Model for Circuit Breakers

Equation I.4, solving for Ibf.....should there not be a term after "log"? All I see is an exponent that I can't really read.

Thanks!

yes indeed the only way the equation makes sense is if it reads Ibf = I1 = 10^(log * I1) not Ibf = I1 = 10*log^ I1

_________________
Michael Furtak, C.E.T.
http://arcadvisor.com


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 7 posts ] 

All times are UTC - 7 hours


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2019 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883