Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 17 replies
  • Subscribers 27 subscribers
  • Views 2984 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Type D MCB 5 Second Tripping Current

Former Community Member
Former Community Member
In BS 7671 17th Edition A3 table 41.3 for type D MCBs gives a 5 second tripping current as 230 x 0.95 / (10In).


When cross referencing time current graphs for type D MCBs I do not get a value of 10In for a 5 second tripping time.


For example see ABB time current graph below giving a current of around 16In for a 5 second trip time.


What is the reason for the difference in values when comparing type D MCB time current charts and table 41.3 in BS 7671 17th Edition A3 for 5 second trip times?

3e6afca19b11a5e876e17f88e8258582-huge-type-d.png
f5deabd80c6b55bd27c69795fb1b7c94-huge-20190722_083103.jpg

Parents
  • Former Community Member
    0 Former Community Member
    @mapj1‍ 


    I emailed ABB and they basically stated that the graph is taken from 60898-1. If what ABB are stating is correct it seems a bit odd that 60898-1 would allow a 5 second tripping current of 13In and BS7671 17th Edition A3 only allows 10In.


    "That Time/Current curve is the tripping curve as defined by the standard EN60898-1, and as such details the upper and lower limits allowable to conform to that standard"


    "The actual trip curve of the ABB MCB is of course much narrower and closer defined.     Specific curves are available and published in our freely downloadable software called Curves, link below :
    https://new.abb.com/low-voltage/launches/selectivity/tools-support/curves"






Reply
  • Former Community Member
    0 Former Community Member
    @mapj1‍ 


    I emailed ABB and they basically stated that the graph is taken from 60898-1. If what ABB are stating is correct it seems a bit odd that 60898-1 would allow a 5 second tripping current of 13In and BS7671 17th Edition A3 only allows 10In.


    "That Time/Current curve is the tripping curve as defined by the standard EN60898-1, and as such details the upper and lower limits allowable to conform to that standard"


    "The actual trip curve of the ABB MCB is of course much narrower and closer defined.     Specific curves are available and published in our freely downloadable software called Curves, link below :
    https://new.abb.com/low-voltage/launches/selectivity/tools-support/curves"






Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines