Transformer current

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Spooner14

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Danville, Pennsylvania, USA
My boss is using a 240 volt primary;240 volt secondary transformer to pick up a neutral wire. The transformer is rated at 10 kVA. We figured the transformer is capable of handling approximately 41.6 amps. My boss said that the transformer can handle 41.6 amps on each leg from line to neutral. And I think the transformer can only handle 41.6 amps total. If you have say 35 amps on line "A" and 40 amps on line "B", won't the transformer fry? My brain is fried from thinking about this.
 
Spooner14 said:
My boss is using a 240 volt primary;240 volt secondary transformer to pick up a neutral wire. The transformer is rated at 10 kVA. We figured the transformer is capable of handling approximately 41.6 amps. My boss said that the transformer can handle 41.6 amps on each leg from line to neutral. And I think the transformer can only handle 41.6 amps total. If you have say 35 amps on line "A" and 40 amps on line "B", won't the transformer fry? My brain is fried from thinking about this.
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No the transformer won't fry. Think of it this way... each half of the secondary winding can handle 5kVA @ 120V.

PS: Welcome to the forum :thumbsup:
 
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Spooner14 said:
My boss said that the transformer can handle 41.6 amps on each leg from line to neutral. And I think the transformer can only handle 41.6 amps total.
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The others have given you the correct answer. But I would like to take this moment to, once again, express the hope that there will come a day when members of our industry stop, once and forever, talking in terms of "total current." It is a non-existent concept. I like Joe's sketch. It demonstrates quite well the concept that current on one leg is the same as the current on the other leg. They do not add up to a value that is twice the value of either current alone.

Welcome to the forum.

 
If you connect the transformer as an autotransformer, you only need one with a rating as high as maximum expected 120 volt imbalance, but that is a different lesson, and could still lead to overcurrent protection problems with the setup. But works great in a pinch if you have a bad neutral problem like an underground lost neutral and you need to have things running before you can fix the underground problem.
 
charlie b said:
The others have given you the correct answer. But I would like to take this moment to, once again, express the hope that there will come a day when members of our industry stop, once and forever, talking in terms of "total current." It is a non-existent concept. I like Joe's sketch. It demonstrates quite well the concept that current on one leg is the same as the current on the other leg. They do not add up to a value that is twice the value of either current alone.

Welcome to the forum.
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Well said!

KVA is KVA is KVA......................:eek:
 
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