Electrical Engineering - Three-Phase Systems in Power Applications - Discussion
Discussion Forum : Three-Phase Systems in Power Applications - General Questions (Q.No. 17)
17.
A three-phase 
-connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I θa = 12 
30° A, what are the polar expressions for the other phase currents?
-connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I θa = 12 30° A, what are the polar expressions for the other phase currents?I θb = 12 150° A, I θc = 12–90° A
150° A, I θc = 12–90° AI θb = 12120° A, I θc = 1230° A
120° A, I θc = 1230° AI θb = 1230° A, I θc = 12120° A
30° A, I θc = 12120° AI θb = 1290° A, I θc = 1290° A
90° A, I θc = 1290° ADiscussion:
8 comments Page 1 of 1.
Aashish Balkrushna Raut said:
1 decade ago
Because in balanced system each phase apart from 120 degree to each other so first phase have phase angle 30 degree, so second have phase angle equal to '30+120=150 degree' in second quadrant and third phase have phase angle equal to '150+120=270 degree' but by using trignometric condition, we can write '270 degree=-90 degree' because it is in third quadrant. So third phase have phase angle '-90 degree' and all phase have same magnitude. So answer is option A.
(8)
Abhilav said:
1 decade ago
For a balanced system the polar sum or the vector sum of all the angles must be equal to zero
Since 1<30+1<-90+1<150 = 0
The system is balanced
For example: A normal 3 phase power from a generating station has the phase difference of 120 each such that 1<0+1<-120+1<-240 = 0
Since 1<30+1<-90+1<150 = 0
The system is balanced
For example: A normal 3 phase power from a generating station has the phase difference of 120 each such that 1<0+1<-120+1<-240 = 0
Laxminarayan said:
1 decade ago
For a balanced network the sum of the phase angle should be 120.
So the correct ans is A.
So the correct ans is A.
Himanshu said:
7 years ago
I think Ib will be -90° and Ic will be 150°.
Nareshdx said:
8 years ago
It's a very good explanation.
Thank you @Aashish.
Thank you @Aashish.
Ramesh said:
1 decade ago
Yes @Aashish you are absolutely correct.
Vignesh said:
3 years ago
Thanks everyone for explaining.
OLA said:
9 years ago
@Aashish you are right.
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