HUGH WILSON
Member
- Location
- Burlington, NC USA
i have not received an answer to my question from yesterday. Obviously I am doing something wrong?
question
- Thread starter HUGH WILSON
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rcwilson
Senior Member
- Location
- Redmond, WA
Welcome to the forum. I assume you are asking about this question, which was answered?
"How do you calculate the horsepower that is available for use, on a 480 volt system, if the KVA of the transformer is known? "
A rule of thumb is 1 HP = 1 KVA. In terms of straight power 0.746 kw= 1 HP. Accounting for typical motor efficiency and operating power factor gets us to the 1 HP = 1 KVA.
So a 100 kVA transformer could run 100 HP motors? WRONG!
Issues like motor starting inrush currents, accelerating times, voltage drops, type of motors, size of motors, type of feed ahead of the transformer (big utility or tiny generator) and existing load on the transformer all have an effect. And we haven't even started to talk about the Code, load calculations, and equipment sizing.
But a rule of thumb again is the transformer should be 3x the size of the largest motor.
Maybe others didn't answer your question because it is a little vague. Kind of like asking if your vehicle has a 400 HP engine how fast can it go?
Give us some more detail about what you are trying to find and we may be able to help.
Good luck!
"How do you calculate the horsepower that is available for use, on a 480 volt system, if the KVA of the transformer is known? "
A rule of thumb is 1 HP = 1 KVA. In terms of straight power 0.746 kw= 1 HP. Accounting for typical motor efficiency and operating power factor gets us to the 1 HP = 1 KVA.
So a 100 kVA transformer could run 100 HP motors? WRONG!
Issues like motor starting inrush currents, accelerating times, voltage drops, type of motors, size of motors, type of feed ahead of the transformer (big utility or tiny generator) and existing load on the transformer all have an effect. And we haven't even started to talk about the Code, load calculations, and equipment sizing.
But a rule of thumb again is the transformer should be 3x the size of the largest motor.
Maybe others didn't answer your question because it is a little vague. Kind of like asking if your vehicle has a 400 HP engine how fast can it go?
Give us some more detail about what you are trying to find and we may be able to help.
Good luck!
rafael rivera
Member
RC ; I think the OP is trying to find out what's the formula to find Starting KVA of the Transformer or the supply system. Which you have already stated, "normally 3X" of the largest motor in some cases.
zog
Senior Member
- Location
- Charlotte, NC
It also helps to have a title to your thread related to the subject, most of us don't look at something with a title like "Question".
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