# Three Phase Systems 1st Time On This Site Need Help Please

Discussion in 'Homework Help' started by TWO SWORD ALI, May 18, 2007.

1. ### TWO SWORD ALI Thread Starter New Member

May 18, 2007
2
0
a star connected load is as shown in the attachment ,when connected to a 400v three phase supply. I have to calculate the line currents and use an accurately scaled phasor diagram to determine the neutral current. If anyone can help me please do thanks p.s. i have no idea of how to even takle this question im not just looking for an answer im looking for an understanding as well thanks

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2. ### recca02 Senior Member

Apr 2, 2007
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i myself havent done much work on an unbalanced network.
but i think u can give it a try this way (if its an assignment question)
i m not sure what happens to voltage across each phase in case of unbalanced condition.

the voltage across phase (line and neutral) wud be 400/sqrt(3)
apply ohm's law to each line and neutral (r-n,y-n,b-n) points.
(note voltage at different phases increasingly lag by 120 degree electrical
taken in order so solve with respective electrical angles)
and arrive at currents in each loop.
apply kirchoff's current law at neutral point to arrive at the current thru neutral.

now take Vr-n as ref and plot the voltage phasors with magnitude and direction according to values found by calculation. similarly plot current in each phase and neutral on the same plot.

at least worth a try what say?

3. ### TWO SWORD ALI Thread Starter New Member

May 18, 2007
2
0
yes thank you ill try it