X/R ratio interrupting

[Mbrooke]

Why would the interrupting rating remain the same across various X/R values?


Also, while 20 is high for a remote station, what is the highest X/R ratio you've seen in the real world anywhere (just curious)?

 

[cuky2000]

Check also the S&C Bulleting 201-190 These short‑circuit interrupting ratings have been determined in accordance with the procedures described in IEEE Std C37.41-2016. S&C recognize that there are many applications where the X/R<15 specified by the standard, higher symmetrical ratings have been determined for many of the fuses listed, for X/R = 10 and X/R = 5.
However, the published SC Interrupting current data is the same even though theoretically as lower the X/R ratio is lower will be the multiplication factor

I do suspect that the reason of constant interrupting current is the result of actual test data that account for the combine effect on the fuse circuit of the magnetic stress by the peak current (physical force for bracing) and the thermal stress (excess heat) associated with the fuse design.

 

[Mbrooke]

Makes sense. Thanks