This is about 3 phase AC

Thread Starter


Joined Dec 30, 2003
Hi there, I am new to this Forum and would be very grateful to anyone who could help me. :)

This should be an easy one for you guys (I think). I'm currently in a 1st year Process Engineering course and due to my background as an international student, I didnt get many courses of electrics in my high school. Anyway, here is the problem (it comes from a sample 1st semester exam):

"Five identical industrial sites are supplied by the standard 3 phase AC mains. In each site, there are inductors in Y-configuration and resistors & capacitors in Delta-configuration. Calculate the total power, cos teta (angle and type) and the Line current. Given are:
U delta = 400 V, f:= 50 Hz, L in Y-conf = 30 mH, R in delta-conf = 8 ohm and C in delta-conf = 200 mikroF"

Anyone wants to give it a try? One other thing: I really prefer if you could do it with non-complex calculation. :p

Thanks! :)


Joined Jan 26, 2004
Okay, just a little confused by what is really happening.

5 sites, each has a delta and Y

and all 5 are connected. The Y is mad of the inductors and the Delta made of resistors and capacitors....

Well I would convert all the deltas to Y's

to do this without complex numbers would be a pain.

Still, I don't see the picture. Maybe you could do this Y-D-Y-D-Y-D to illustrate it a little better


Joined Nov 17, 2003
Tada is right, the only real way is to use complex numbers to derive your impedances in the configurations, then manipulate the star-delta configurations in the network you have.

I can post up some formulae for calculating impedances and for th transformations if you like, but it would helpful if you could give us an indication of how you network interacts, i.e. Y-D configuration.