NCEES power # 113

[WantsPE]

Can someone please explain this to me. How did they come up with 1/180, 1/90 seconds and so on?

Thanks

 

[Flyer_PE]

It's based on a 60 Hz 3-phase wave form. One cycle for each phase will be 1/60 seconds in duration. Since there are three phases being considered, there will be three peaks for each cycle. One at 1/3(1/60) = 1/180 the second will be at 2/3(1/60) = 1/90 etc.

 

[WantsPE]

Thank you. That makes sense now