a 3ph 480v motor tripped a breaker.a worker saw this and re-set the breaker.a short time the worker saw the breaker tripped again and tried to re-set the breaker.at this time the panel exploded knocking the worker to the ground.he recieved a severe electrical shock and burns which hospitalized him and put him in a burn unit.
how many times must a breaker trip before you call an electrican? 2 sure isnt good.
You did not include enough information to provide an answer which is applicable to your situation.
Circuit breakers are tested and then listed based on:
Rated voltage
Applied voltage
Frame size
Trip unit type
Rated continuous current
Applied continuous current
Rated short circuit fault current
Applied short circuit fault current
Short circuit impedances
Type of fault (i.e. bolted, three phase)
Number of poles clearing the fault
Also you need to include the electrical and mechanical history of your breaker. This history should include the number of no-load operations, the number of full-load operations, and the number of short circuit operations.
In general, I believe breakers are only "rated" for 2 operations at their maximum short circuit rating.
In general
OSHA says you must invetigate the cause of the trip before the breaker is reclosed.
Breaker was probably tripped and reset many, many, many-many-many times before this scenario.
Sounds like the frame failed to contain the arc (probably a bolted fault condition on the load side),
Or,
The AIC of the frame was highly exceeded,
Or,
The frame fell apart and caused an arc fault,
Or,
All of the above.
As pointed out by Don, find out why a breaker is tripping first. Then only after correcting the problem would the breaker be reset.
If it trips again, there are more problems to look for.
When 480 VAC Power Circuits are tripping, be REALLY careful when resetting breakers!!!
Find the fault(s) first!!!
Reset the breaker last!!! Do it only once!!!
Arc faults are very mean Animals!!! They are like Badgers:
Very belligerent, extremely fast, and most of all, very unforgiving!!
Scott35