# 3 Phase Voltage Help

Discussion in 'Homework Help' started by dmarullo3, Mar 26, 2013.

1. ### dmarullo3 Thread Starter New Member

Mar 26, 2013
2
0
Looking for some help with a hw problem. Having some trouble with AC phase relationships. In this problem im having trouble determining the phase sequence. I think i can get the angle from the frequency the three voltages are at. Help would be greatly appreciated. Ive attached an image of the problem.

File size:
292.2 KB
Views:
17
2. ### Paulo540 Member

Nov 23, 2009
188
0
If Vb -> Vc -> Va, you can always reconfigure it to be a b c. Might make it easier.

Also, it might help to note where the zeros cross on the chart instead of the peaks.

I assume you are able to do the RMS and leg voltage calcs at this point. ?

3. ### dmarullo3 Thread Starter New Member

Mar 26, 2013
2
0
yes i have the RMS voltages, i know the between the three voltages they are 120 deg apart for the phase voltages and the line voltages are the same only separated by 30 deg.

4. ### panic mode Senior Member

Oct 10, 2011
1,657
468
there are only two sequences - abc and bac
since this is periodic, it repeats over and over so abc sequence looks like
abcabcabcabcabc...

you can see inside it 'bca' so this is 'forward' sequence

if you swap any two phases, you get bac:
bacbacbacbacbac...

btw. 'bac' is similar to *back* (or reverse) sequence