open delta transformer

[Flyer_PE]

So in response to that, do they want you to think like a student or any engineer? I could as an engineer choose to use a 25 kVA knowing that it will be slightly overloaded, but that it could be well within what I find acceptable for use and it is a very common size. As a student I would say "Definitely it has to be a minimum of 28.9 kVA because the math says so" I suppose it goes back to "Read the question carefully!"

Here's my thought on this in the exam:

It's a multiple choice test. You don't get to write any kind of justification about choosing to live with a slightly overloaded transformer. If given a choice between a 25 and a 30 for this application, the 30 would get my vote. The only way it wouldn't is if the question got into the economics of how much the price difference is vs. service life etc. However, going there would result in a question that couldn't be answered in six minutes or less.

 

[Kahrlo]

The easiest way to do this is to remember that in an open delta connection (2 transformer), that the maximum power that you can have is only 87% of the total kVA of the transformer. Therefore, the minimum power that each transformer must have is

50kVA/2/0.87= 28.735 kVA for each transformer

 

[NoobEE]

The easiest way to do this is by just multiplying the Rated Power by sqrtof3 divided by 3 ..

[ 50 KVA x sqrtof 3 ] / 3 = 28.86 KVA ...

do you still want me to explain why I did it this way?

 

[NoobEE]

The easiest way to do this is to remember that in an open delta connection (2 transformer), that the maximum power that you can have is only 87% of the total kVA of the transformer. Therefore, the minimum power that each transformer must have is
50kVA/2/0.87= 28.735 kVA for each transformer

..

kindly double check on your equation Sir.. I apologize but it doesn't equate to 28.735 based from your equation