Maximum Interrupting Time - HFW Breakers

What seems to be problem? Max. interrupting time vs multiple of the nominal current curve is given in the graph. Just read it.
You need to know only the rated (nominal) current of the breaker.

 

The Max time is the curve(line) - for any current level you then have to find the corresponding point on the curve. However - these curves are most useful when you superimpose the various elements onto one curve, you can then see the coordination between the various elements. For example -- if there are up stream fuses they will have a similar Time Curve - you would want the down stream items ( cables, motors) to be protected by this device and ideally not the fuses.

 

Does 5.5 Sec sound like it is instantaneous? Not mocking your post - but asking you to think about the info. The Long time will be for general overloads and often based around 3 to 5 x the FLA. ( It has been a while since I did these) - however you need to ensure that even at 150% the breaker will eventually trip to prevent the motor from overheating. Smaller motors the shorter the time they can be in overload.

As for the instantaneous(see note below) - you need to make sure that the LRA hits that part of the curve, but noting some motors ( particularly high efficiency) can hit LRA on hard line starts.

The motor OEM will often provide the same format time current curve to help with this coordination.

Often the Locked Rotor coordination really is referred to a Short Time (not instantaneous) - in general terms Long Time is for Motor overload, Short time ( locked / seized motor) has a small fixed amount of time to allow for starts, and true Instantaneous is for electrical short circuits / faults ( so there is no intentional time delay on the trip).

 

So you mean 0.013 Seconds ? Wont that be at 80X or 3200A.. as you pulled the line out. --

If the LRA is 143A = 3.6X ( of the 40A) --- as I read this you are up to 40 Secconds - a small motor like this probably can not survive 40 Sec locked rotor. Another way to think of this for a 480V 3PH motor....( 143 x 480 x Srt(3) )= 119 KW of heat ! being dumped into the windings of the motor!.....

I would only want LRA to exist for 1-2 Seconds at most in a typical application.