Question

Q2.A three phase system supplies a load of 30KW at p.f. of 0.8 . The line

voltage is 250V . If load is connected in 1.star 2. Delta and find line

current and phase current.​

Answer 1

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Explanation:

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Answer 2

Given:

power P = 30KW  = 30000 W

p.f. = 0.8 V

$V_{line}$ = 250 V

To find:

1) line current $I_{line}$ =?

2) phase current $I_{phase}$ =?

Explanation:

1)

The line current is the ratio of power to the line voltage.

$\displaystyle I_{line} = \frac{P}{V_{line}}$

       = $\displaystyle \frac{30000}{250}$

 $\mathbf{I_{line}}$ = 120 A

The line current of line voltage 250 V is 120 A.

2)

The phase current of star delta transformation is a ratio of line current to the cube root of 3.

This phase current is given by

$\displaystyle I_{phase}=\frac{I_{line}}{\sqrt3 }$

          = $\displaystyle \frac{120}{\sqrt{3} }$

$\mathbf{I_{phase} =69.28}$ A

Hence the phase current of star delta transformation is 69.28 A.