# Don't understand 3 phase source/load theory

Discussion in 'Homework Help' started by zicker, Sep 21, 2009.

1. ### zicker Thread Starter New Member

Jul 15, 2009
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0
I'm studying 3 phase systems and there are important pieces that aren't explained that well. I don't understand why when transforming Y to Delta loads/sources you need to divide by sqrt.3 for voltage and current and dived by 3 for delta load to Y load. maybe doing a problem would help.

Here's a HW problem I can't figure out.

1.24: The load on a 460-V, 60hz, Y-connected, balance three-phase source consists of three equal Y-connected impedances of 100+ j100 ohm and three equal delta-connected impedances of 300-j300 ohm. Compute the line current, power, and the power factor for the total load.

There's no picture of the circuit and I have no clue how to handle two different types of loads. What do I do?

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
782
If it's homework then you should post it on the homework forum.

Jul 15, 2009
8
0

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
782
You'll probably find many sources of info on the web or in text books concerning 3-phase loads.

I've attached a pdf diagram and some explanatory calculations - you'll need to try something like this if you are hoping to get a grasp on the concepts. In particular you should have a sound understanding of phasor diagrams and how to draw them in relation to a given circuit.