I need help with a test question

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fletcher

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Detroit Michigan
i don't want anyone to give me the answer....i just dont understand the question.

i want to place out of a 2 credit hour residential wiring class at the local community college. so i am taking a take home test. i have an apprentice letter verifying 1 year of residential wiring.

the question is:

"describe four electrical power systems for where and how each is used in residential and light commercial systems."

what do they mean by "power systems"
 
Re: I need help with a test question

I don't understand the question either. The word "for" seems out of place, and I can't tell what it means.

My best guess is the same as Ryan's second guess.

120/240 single phase is one type of power system, used in residential. 120/208 three phase is another type, and it is used in many commercial and industrial applications. If you interpret the question as meaning these sorts of power systems, I think you will be on the right track.
 
Re: I need help with a test question

for what its worth, I started to answer earlier, but had the same thoughts and felt, rightfully so, that folks like charlieb could give u better answers than I. In "word searching" the code , like them, I find it can be either different voltage systems or different types....my feeling is as charlie & Ryan state... 120/240, 208Y/120, 480Y/277, deltas, etc. good luck.
 
Re: I need help with a test question

Call the school and ask somebody. You have a right to do so. Just as you would if you were sitting in a classroom taking a test. It sure beats guessing.
 
Re: I need help with a test question

I would assume that the four power systems are as follows:
(1) 120/240 volt, 3-wire Edison system.
(2) 208/120 volt, 3-phase wye, 4-wire system.
(3) 480/277 volt, 3-phase wye, 4-wire system.
(4) 240/120 volt, 3-phase delta, 4-wire system.
 
Re: I need help with a test question

Utility
Battery
photovoltaic
generator
Fuel Cell
Isolated
SDS Transformer
Stand by
Emergency
3-Phase
Single Phase
Low voltage
technical

These are all the power systems the NEC mentions, Not including the one's John has posted.
Now which four ????
 
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