Recent content by DunceKirchhoff

Ok thanks I got you. Well explained.

So basically I have put vab, vbc and vca where vao, vbo and vco should be? And the phase angle is -30 instead of 30?

I am wrong sorry, yes it has asked me to use vab as a reference. So vab=0 degrees Vbc -120 degrees Vca 120 degrees Whats the phase voltage?

Hi Neil Sorry will do that in the future. Yeah usually the ref is 0 degrees agreed. But in this question the line voltage is not given but the phase voltage Vao. So given that information I have tried to work it out. Also the line voltage leads the phase voltage by 30 degrees. Could be wrong

Anyone??

http://i59.tinypic.com/727ole.jpg My answers http://i59.tinypic.com/mkzvqp.jpg Can some see if I am going in the right direction, thanks.

A 50 Hz ac three phase supply has a peak voltage of 100 V. Calculate the instantaneous voltage of each phase at a time of 7.5 ms. Looked all over google and can't seem to find an equation for this? Can anyone point me in the right direction?

It equals 1. Yip I get you thanks. Its just the way it was laid out that got me.

I can't see any indication on how they have chosen which are angles which. Its important to know as it obviously effects the overall answers.

The phase angles are given here because it is a worked example. Questions there after do not give you these angles, instead they say for example use Vab for reference.

Yes but just by looking at the diagram you must be able to tell which is which? Using Vab as a reference, the reference is always 0 degrees. So if Vxy is used as a reference in another question that will also be 0 degrees. How do I find out the other two?

So for the top one the two minuses become a positive?

Ib= (-12.4-j6.88)-(9.57-j6.38) Ib= -12.4-j6.88-9.57+j6.38 Ib=(-22-j0.5)A Why does the -j6.38 become +j6.38? Ia=(9.57-j6.38)-(0.454+j13) Ia= 9.57-j6.38-0.454-j13 Why does the +J13 become -J13? Thanks

http://i60.tinypic.com/nmntpj.jpg How do you differ what angle for example Vab, Vbc, and Vca are? I notice the reference angle is always 0 degrees but how can you tell for the other two? Thanks in advance.

Thanks that helped!