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why circuit breaker closing time is always higher then
tripping / opening time.
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Answer Posted / michael von zechlin
Neither of you are correct and for that matter who really
cares which is greater?
The opening and closing times of circuit breakers are
based on mechanical variables such as charging spring
tension, contact gap, trip mechanism delay etc. The goal
for a circuit breaker is to make or break the contacts as
quickly as possible to either slam the device on line or
open the contacts quickly enough to minimize the time that
an arc exists at the contacts.
What is significant are two measurements that provide an
indication of what the actual operating characteristics of
the circuit breaker are.
First, connect the contacts in series with one another
and a timer such that the circuit goes timer, 1st contact
set, 2nd contact set, 3rd contact set timer. (In one out
the other). Time the opening and closing of the circuit
breaker contacts. This will provide the fastest set of
contact make/break time.
Second, connect the contacts so that they are in
parallel with eachother record the value (This is the
average open/close time).
Once you have done this several times, say about 20,
take an average of each of the first/second measurement
times. Each manufacturer of circuit breakers has published
values for what those readings should be (average.
The significant readings of circuit breaker testing are
not usually related to the timing of the contacts, yes the
contacts can cause a motor to briefly single phase for less
than maybe 2 complete power cycles but not enough to really
matter, the significant measurements are those of mico-ohm
or millivolt drop across the contacts and closing spring
tension.
| Is This Answer Correct ? | 12 Yes | 2 No |
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