commercial electrical plans examiner test question

[JamesJohnston]

test question is :
a 3 phase wye system has 60 ,80 ,70 on each phase , what is the unbalanced neutral .
available test answers are : 10 ,50 ,80 ,150


my answer to this question is 17.3 however this is not available in the test

 

[infinity]

Can you show your math?

Here's my guess, from the answers given they think that the answer is 10. I think they used this formula, subtract 60 amps from all three numbers and you left with 0, 20 and 10 amps per phase the difference between 20 and 10 is 10.

 

[synchro]

I agree with Infinity that they probably were thinking along the lines that he mentioned. But your answer is correct. If this was a real test and there wasn't a "none of the above" selection available, the only choice left is to pick the closest answer that they provided which is 10.

 

[infinity]

I agree with Infinity that they probably were thinking along the lines that he mentioned. But your answer is correct. If this was a real test and there wasn't a "none of the above" selection available, the only choice left is to pick the closest answer that they provided which is 10.

That's the thing with test questions often you have to decipher what the person writing the question had in mind even when the answers all appear to be incorrect. In this example the other three answers are not even close so they could be discarded leaving you with only the closest answer 10.

A few decades ago when I took the state electrical licensing exam they gave us a form to write down a question(s) that was felt to have no correct answer for situations like this.

 

[JamesJohnston]

Thank you for the assistance.