Primary Fusing for Transformers

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gobblerhuntr

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I am trying to create chart for fusing of transformers we typically use and would like a proof read please of the calcs. Do the calcs look correct for fusing each phase of the three phase banks?? Any ideas are appreciated.

I attached a .doc witht the calcs.
 
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dorymill

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I spot checked a couple of your numbers and they are fine. One thing to remember is that all fuses have a particular current vs time curve. If you have a situation that may involve a relay operated switchgear or vacuum circuit breaker that operates off of relay settings based on CT ratios you need to be sure to coordinate the relay so that it does not exceed your fuse curve. Otherwise you will loose the fuse and the switchgear will not get a chance to protect the circuit. Curves for fuses are available and if the full load KVA of the transformer is very close to your demand some thought should be given to the types of loads and starting currents of machines on the system.
 
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