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BAIMWO
Member
Indonesia
19 Posts |
 Posted - 12/14/2008 : 09:51:15
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I have been recently trying to up my knowledge in Transformer ratings.
the Problem is..
a transformer has 450 KVA Rating the secondary is 480 Volt,,in the name plate 450 KVA = 13800 Volt
X1-225 kva = 480 V
Y1-225 kva = 480 V
and the load conected with X1 connection is 480 V ,the load is reda motor 50 Hp
MY QUESTION IS...? What's size fuse links that be used............... 225 KVA ( 6,3 slow fast ) or 450 KVA ( 10,4 slow fast/25 K )
please help me?
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WFO
Active Member
USA
83 Posts |
Posted - 12/27/2008 : 09:41:28
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Not sure that this is the answer that you're looking for, since you asked about sizing a fuse on Kva instead of amps.
The Kva rating of the transformer applies whether you are talking primary or secondary, star or delta, as long as you use the formula..
Kva divided by Phase to Phase volts divided by 1.73 (the square root of 3) equals the per phase current.
If you use the primary volts, you'll be calculating primary amps. Use secondary volts, your're calculating secondary amps. I think the amps is what you will need for the sizing of your fuses.
If I'm wrong, I apologize in advance 
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bytemylobster
Avid Member
Canada
409 Posts |
Posted - 11/25/2009 : 08:22:00
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For a dry-type transformer rated at 750 volts or less:
CEC #26-256(1): Except as permitted in (2) each ungrounded conductor of the transformer feeder or branch circuit supplying the transformer shall be provided with overcurrent protection rated or set at no more than 125% of the rated primary current (amps) of the transformer, and this primary overcurrent device shall be considered as protecting secondary conductors rated at 125% or more of the rated secondary current.
(2) is if you have secondary overcurrent protection added.
(3) Where a value not exceeding 125% of the rated primary current of the transformer as specified in (1) does not correspond to the standard rating of the overcurrent device, the next higher standard rating shall be permitted. |
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fuse size
