PE power question

[Toilalong]

For Load, Motors, Generator
lead PF = negative Q ; lag PF = positive Q

But sometimes when I do practice problems I see some places claim lead PF = positive Q ; lag PF = negative Q for Motors and Generators.

I'm confused, any help to clear things up a bit will be greatly appreciated.

-Thanks,

 

[KatyLied P.E.]

I believe it's a matter of which convention you choose. GA Tech's PE prep course's convention is reactive power that is capacitive (leading) is negative while inductive (lagging) is positive. Their course specifically uses the phrase "by our convention" so evidently other sources choose differently. I like to think of it in terms that the electrical system is by default inductive and I then equate "positive" to that. Capacitive acts as a "negative" to that to correct the PF. That may sound kind of strange but it helps me understand.

 

[KatyLied P.E.]

I'd think the important thing is to stay consistent whichever convention you choose. also the problem would most likely indicate which convention you should use for that case.

 

[Dark Knight]

I'd think the important thing is to stay consistent whichever convention you choose. also the problem would most likely indicate which convention you should use for that case.

x2

 

[cupojoe PE PMP]

I'd think the important thing is to stay consistent whichever convention you choose. also the problem would most likely indicate which convention you should use for that case.

x2

+1 you would likely have to give your answer as leading or lagging, not positive or negative, so I think it would be more how you set up the problem.