Short Circuit
Short Circuit
(OP)
If a transformer feeds the MCC, then should the MCC be sized based on the "full" short circuit current from the transformer?
What if the transformer secondary has a current limiting fuse? Should the MCC still be sized based on the "full" short circuit current from the transformer, or is it possible to take the current-limiting effect of the upstream fuse and size the MCC for less?
What if the transformer secondary has a current limiting fuse? Should the MCC still be sized based on the "full" short circuit current from the transformer, or is it possible to take the current-limiting effect of the upstream fuse and size the MCC for less?






RE: Short Circuit
Yes.
No.
RE: Short Circuit
*If applicable in your jurisdiction.
RE: Short Circuit
RE: Short Circuit
RE: Short Circuit
Rafiq Bulsara
http://www.srengineersct.com
RE: Short Circuit
RE: Short Circuit
That was clearly answered by davidbeach in his very first response. I was only responding to what was asked in your follow up question.
Rafiq Bulsara
http://www.srengineersct.com
RE: Short Circuit
As part of a list series rating combination (listed as a result of successful testing, no calculated listings) a current limiting device may be used to increase the rating of another device in the same listing. It does not reduce the fault current to the lower rating, it increases the lower rating the the value in the listing.
RE: Short Circuit
The thing in question appears to be some kind of control panel with switching devices and possibly a breaker or fuses. At any rate, it's likely not just a capacitor. You're not telling so we really don't know for sure. This "capacitor" could have devices where the series rating could be used. Also, the switching devices (contactors) might have a higher fault rating if you switch the panel to fuses instead of a main breaker. You'll have to investigate this stuff and find out.
Also, your capacitor kA rating terminology is still off. I've never seen a capacitor (just the capacitor can) with a kA rating. raghun described capacitor rupture in your other thread. If the panel containing the capacitors has a kA rating then it is due to the other devices in it.
RE: Short Circuit