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  1. What is the posit ive sequence currents in a three phase system, when the original phasors at which are Ia = (12 + j6), Ib = (12 – j 12), Ic = (– 15 + j10) ?
    1. 14.8 Amp.
    2. 16.2 Amp.
    3. 18 Amp.
    4. 10.2 Amp
Correct Option: A

Ia = (12 + j6)
Ib = (12 – j 12) = 16.97 |45°
Ic = (– 15 + j 10) = 18.02 |46.3°

Ia1 =
1
(Ia + αIb + α² Ic)
3

=
1
[(12 + j6) + 1|120° 16.97|- 45° + 1|240°. 18.02|146.31°
3

=
1
[(12 + j6) + 16.97|75° 18.02|146.31°
3

=
1
[(12 + j6) + 16.97|75° 18.02|386.31°
3

=
1
[(12 + j6) + 16.97(cos 75° + jsin 75°) + 18.02(cos 386.31° + j sin 386.31°)]
3

=
1
[12 + j6 + 4.392 + j 16.392 + 16.16 + j 7.06]
3

=
1
(32.55 + j 30.38) = 14.84 |43.02°
3



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