What are the difference between C-Curve and D-Curve for
MCB's.

Answer Posted / nimda

The magnetic trip for a B-curve MCB will not operate below 5
times rated thermal current but will surely operate
instantaneously above 10 times rated thermal current.
The magnetic trip for a D-curve MCB is will not operate
below 10 times rated thermal current but will surely operate
instantaneously above 20 times rated thermal current.
The choice between B-curve and C-curve depends on the loads
ratio between load inrush current and load running steady
state current.
For the same running load current if the cable is long then
a D-type MCB may need a larger cable cross sectional area,
compared to a C-type MCB, just to ensure that sufficient
fault current always is available for operation of the
instantaneous magnetic trip.

Is This Answer Correct ?    31 Yes 8 No



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