# 3 phase wye wye delta R C L circuit

Discussion in 'Homework Help' started by de_rock, Mar 22, 2009.

1. ### de_rock Thread Starter New Member

Mar 22, 2009
2
0
Ok well i am having troubles with question 5 i have a pretty huge test tommorow, and was hoping somebody could help me out just click on the attachment and take a gander.

Thanks

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2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
Perhaps show how far you have got with your answers on this - it's a lot of work for someone to do without first seeing your attempt.

3. ### de_rock Thread Starter New Member

Mar 22, 2009
2
0
Yea i realize it is kind of alot of work but even just the formulas needed would be a ton of help.
my Professor told me this is on the test and the internet has for some reason not worked out for me this time.

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
OK - I'll just give my method for RMS current magnitudes only. I'll use the notation |I| to indicate the magnitude of I.

3-phase loading is balanced so all line currents balance.

For IR:

|IR|=(Vline/√3)/R where Vline = 440V

For IXC1:

|IXC1|=(√3 x Vline)/Xc where Xc=1/(ωC)

For IXC2:

|IXC2|=Vline/Xc

For IXL:

|IXL|=(Vline/√3)/XL where XL=ωL

For I2:

|I2|=||IXC1|-|IXL||

i.e. subtract the reactive current terms since they are in anti-phase

For IT:

|IT|=√(|IR|^2+|I2|^2)

i.e. vector addition of real and reactive current values.

Hope that's of some help. I'll leave the rest to you.

5. ### Jennifer New Member

Mar 23, 2009
3
0
was that of any help to you? I haven't quite gotten to motor controls yet, but that is where I'm heading. He gave you the formula to work the problem out. Good luck on your test.