power in star connection

Hello



I looked for a good forum which I can use for my specific questions.

I hope I am right here.

English is unfortunately not my first language, but I am working on improving it. So please have understanding for it.



I need help in three phase drive technology. I read in my book that power is defined by



p1 = u*i = u*sin(wt+phi)*i*sin(wt)



Now I ask myself why the first term of sin() contains a +phi and the second term does not.

I mean in the star connection for example u and i have an angular phase shift. So why is also in the second term not a +phi?