# Need help with 3 phase q

Discussion in 'Homework Help' started by trx, Sep 27, 2009.

1. ### trx Thread Starter New Member

Sep 27, 2009
1
0

Can anyone pleae help me with this questione.. How do I fine the impedance of the circuit ???

A factory draws a total of 415kVA from a 2.4kV (line voltage) 3-phase supply. If the plant
power factor is 0.875, calculate:
a. The impedance of the plant per phase
b. The phase angle between the line-to-neutral voltage and the line current​
c. Draw a phasor diagram showing the voltages and currents of the three phases

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
There are a few approaches but I normally take this one

* Calculate the VA load per phase - Q
* Calculate the line-to-neutral voltage - Vln
* Calculate I line = Q/Vln
* Impedance per phase Zph = Vln/I line
* Calculate current phase angle (θ) with respect to Vln where θ=acos(pf) and assume it is lagging pf
* Draw your phasor diagram remembering that in a balanced 3-phase system the line currents and their phase angles will be equally balanced.