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 6 replies
  • Subscribers 27 subscribers
  • Views 522 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

Tripping Curves and M.C.B.s.

Zoomup
A Schneider catalogue that I have has a technical section on tripping curves. It discusses a C20 M.C.B. It states that it will interrupt a current of 100 Amps (20 times the rated current) in:


0.45 seconds at least


6 seconds at most.


For tripping currents exceeding 20 times the rated current the time-current curves do not give a sufficiently precise representation. The breaking of high short circuit currents is characterized by the current limiting curves, in peak current and energy.


The total breaking time can be estimated at 5 X the value of the ratio (I2t)/(I)2. Is that I squared t divided by I squared? Just what is that?


Z.
Parents
  • 0
    I was wondering what the horizontal "I/In" meant. "In" would make sense. I presume that it means I or In, rather than I divided by In.

    Without looking at the context I suspect they mean the fault current divided by the rating of the device - i.e. how many "times" the rating we're talking about. Often that approach is useful for protective devices as many currents are defined as multiples of the nominal rating - 1.13x or 1.45x or 5x or 10x. Often that means you can produce one graph or table for the whole range of devices rather than having to produce one for each rating.

       - Andy.
Reply
  • 0
    I was wondering what the horizontal "I/In" meant. "In" would make sense. I presume that it means I or In, rather than I divided by In.

    Without looking at the context I suspect they mean the fault current divided by the rating of the device - i.e. how many "times" the rating we're talking about. Often that approach is useful for protective devices as many currents are defined as multiples of the nominal rating - 1.13x or 1.45x or 5x or 10x. Often that means you can produce one graph or table for the whole range of devices rather than having to produce one for each rating.

       - Andy.
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