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Tripping Curves and M.C.B.s.

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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.
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    I like the tripping curves on page 11/5 of the Schneider catalogue. The graphs show time (S) as the vertical line and I/In and the horizontal line. Curves for types B, C and D devices are shown with coloured areas for the operation of their 3 to 5, 5 to 10 and 10 to14 times In ranges. Applicable  AREAS are shown which helps clarity. 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.


    Z.
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  • 0
    I like the tripping curves on page 11/5 of the Schneider catalogue. The graphs show time (S) as the vertical line and I/In and the horizontal line. Curves for types B, C and D devices are shown with coloured areas for the operation of their 3 to 5, 5 to 10 and 10 to14 times In ranges. Applicable  AREAS are shown which helps clarity. 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.


    Z.
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