- #1

Mathn00b!

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## Homework Statement

Hello, I am given the following problem.

A balanced three phase 4 wire supply has r.m.s. line voltage of 415V and supplies a star-connected load made of 3 impedances:

Za = 10 - j10; Zb = 10 + j10; Zc = 0 + j8;

Calculate the current phase and neutral currents, also the total power dissipation. [NOTE: Assume that Va is drawn vertically up, i.e. its phase angle is 90]

## Homework Equations

I've used V

_{line}= √3 x V

_{phase}

Also, P = E

_{a}x I

_{a}x cos(Φ

_{a}) + E

_{b}x I

_{b}x cos(Φ

_{b}) + E

_{c}x I

_{c}x cos(Φ

_{c})

## The Attempt at a Solution

Please find the attached file, as my solution to the problem. As it could be seen the answer is quite different. In fact their answer is just the sum of the 1st two bits of the power, ignoring the last one. I assume they used cos(90) to get 0 and hence lower power. If this is the case, then the Z

_{c}should look like 8∠90° .

But isn't it found from the equation : Z

_{c}= √0

^{2}+ 8

^{2}∠tan

^{-1}(8/0) ?

http://i1375.photobucket.com/albums/ag441/gl0ck1/StarLoad_zpslnhuotig.jpg

#### Attachments

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