# Balanced 3-phase circuit

Discussion in 'Homework Help' started by hitmen, Jan 8, 2010.

1. ### hitmen Thread Starter Active Member

Sep 21, 2008
159
0
Q1) The question is about a 440-V balanced 3-phase Y-connected circuit.
May I ask is the 440V phase voltage or line-to-line voltage and why?

Q2) I know the equation Iline = Vphase / (Zline + Zload)
Why is the voltage in phase but the current is line to line?

2. ### JDT Well-Known Member

Feb 12, 2009
658
85
Q1 In a balanced 3-phase circuit the voltage is line to line. The centre of the Y (or star) is not connected. (sometimes it is connected to earth)

Q2 Don't forget that the currents in each of the 3 loads are 120deg phase difference. The current in each line is the phasor resultant of the current in two loads.

Hope this makes sense!

3. ### hitmen Thread Starter Active Member

Sep 21, 2008
159
0
Hi JDT thanks for the help

Regarding A what happens if the structure is delta shape instead?

I dont understand b. Dont 120+120 degrees = 240 degrees?