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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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    If you look carefully, the second I is wearing a little hat, thus: Î. It is not defined in the text nor in section 2 of BS 7671.
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    If you look carefully, the second I is wearing a little hat, thus: Î. It is not defined in the text nor in section 2 of BS 7671.
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