DISCONNECT SWITCH

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epe_guy

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Would a 200 amp continous rated primary disconnect switch be adequate for a 500kva transformer (2400v delta to 480 delta0? My primary current is 125 amps. I was thinking of going to my next option of 400amp due to the load is 6 \75 hp motors plus other minor loads, however switch is a bit more costly.

thanks
epe_guy
 
Re: DISCONNECT SWITCH

mmmmmmmmm, 2400v primary and a primary disconnect switch. 240v is medium voltage, what disconnect did you have in mind? S&C, C-H type WLI, or?
 
Re: DISCONNECT SWITCH

I'm showing that the 2400v pri. 3ph FL current of a self cooled 500kva power xmr to be 120a. The suggested minimum primary CL fuse current rating is 200a which represents the smallest fuse possible that will withstand transformer inrush (12xFLA for 0.1sec) and will be able to handle temporary overloads (133% of FLA).
And expulsion fuse would be a 200E.
I would understand that you are providing secondary OC protection and, as such, the pri. protection does not need to provide OC protection also but is intended to take the transformer off line should the transformer fail, i.e. short circuit protection to limit damage to the failed transformer but yet not blow under normal load conditions.
 
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