Network Theory

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Network Theory

Postby ambicaraina » Sun Nov 13, 2011 8:26 pm

A balanced 3-phase star connected load is fed from a 208 volt 3-phase supply each leg has a load of 15+j20
what will be total power?
a) 1036.8
b) 1040
c) 1030
d)none
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Re: Network Theory

Postby ck_gagan » Sun Nov 13, 2011 11:16 pm

ambicaraina wrote:A balanced 3-phase star connected load is fed from a 208 volt 3-phase supply each leg has a load of 15+j20
what will be total power?
a) 1036.8
b) 1040
c) 1030
d)none



Total Power = square root of (3) x VL x IL x cos (fi)

= 1038.33 W (Option d is correct)

Thanks
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Re: Network Theory

Postby ambicaraina » Thu Nov 17, 2011 1:07 am

whats the value of vl, il and fi in your case as i am getting 360.26V, 14.41A, and 53.13deg
and my ans i s wrong sm were plz help me out.
and ya thanks for reply..
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Re: Network Theory

Postby ck_gagan » Fri Nov 18, 2011 9:57 am

ambicaraina wrote:whats the value of vl, il and fi in your case as i am getting 360.26V, 14.41A, and 53.13deg
and my ans i s wrong sm were plz help me out.
and ya thanks for reply..


Sorry I could not notice your post inadvertently.

Any way VL = 208 V only. (Remember By convention specified voltage is rms value of line voltage , unless specified in particular)

Vph = VL/square root of (3)

|Z| = 25

IL = Iph = Vph/|Z| = 208/(square root of (3) x 25)

Cos(fi) = 3/5


P = square root of (3) x VL x IL x cos (fi) = (208 x 208x3)/125 = 1038.336

Hope you get it this time

Thanks

C K Mishra
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