BREAKERS TRIP

[domnic]

Is their a ul listed chart that tells how long a breaker can be over loaded before it trips?

 

[ron]

Each breaker model has its own chart.

For example here are some from GE

https://www.geindustrial.com/your-business/consulting-design-engineer/time-current-curves

 

[jim dungar]

Is their a ul listed chart that tells how long a breaker can be over loaded before it trips?

What you are looking for is called a Time Current Curve. You can it from the manufacturer of the device.

Sounds like you had an incident, do you want to share the details?

 

[GoldDigger]

Also note that there are two curves on the graph, the must open and the must hold values. Between the curves is the individual variation among breakers as to when they will actually trip.

 

[templdl]

Is their a ul listed chart that tells how long a breaker can be over loaded before it trips?

Are you looking to compare the trip curves in an attempt to coordinate breakers? Then get a copy of the trip curves from the manufacture Or, simply to find out what over current is required to trip the breaker? Then simply refer to NEMA AB4.
Should you be trying to varify the calibration of a breaker in the field there is no legitimate way to do testing other than with an extremely expensive test equipment.
That said a good place to start is with NEMA AB4 which is the "Guidelines for inspection and preventitive maintenance of molded case circuit breakers used on commercial and industrial applications."
5.5 includes: Inverse time current trip test. This section shows the set up required to do the test. Please note that this is not intended as as vaification of the trip curve itself.
Table 5-3 Values for inverse time trip test.
As an example from this chart breakers with a rating of 101-150a @250v or less the maximum trip time is 200sec and 275sec @251-600v
226-400a is 300 and 350sec respectively.
Since an instantaneous trip test is not practical because it requires either a run up or pulse test attempting to do this test may severely damage the breaker in the process since measuring the peak current is very difficult without special equipment.

 

[templdl]

Are you looking to compare the trip curves in an attempt to coordinate breakers? Then get a copy of the trip curves from the manufacture Or, simply to find out what over current is required to trip the breaker? Then simply refer to NEMA AB4.
Should you be trying to varify the calibration of a breaker in the field there is no legitimate way to do testing other than with an extremely expensive test equipment.
That said a good place to start is with NEMA AB4 which is the "Guidelines for inspection and preventitive maintenance of molded case circuit breakers used on commercial and industrial applications."
5.5 includes: Inverse time current trip test. This section shows the set up required to do the test. Please note that this is not intended as as vaification of the trip curve itself.
Table 5-3 Values for inverse time trip test.
As an example from this chart breakers with a rating of 101-150a @250v or less the maximum trip time is 200sec and 275sec @251-600v
226-400a is 300 and 350sec respectively.
Since an instantaneous trip test is not practical because it requires either a run up or pulse test attempting to do this test may severely damage the breaker in the process since measuring the peak current is very difficult without special equipment.

I overlooked to include what current this test should be run at which would be 300% of rated continuous current of the breaker.