Simple AC circuit

Hello guys,
I was solving simple AC circuit given in this figure. After I solved it manually, I tried to check and confirm results with Electronics Workbench Multisim 8. In the attached picture you can actually what ampermeters will show, but the problem is that I got exactly opposite results.

Current RMS in upper rung was 11.4 A, while current in bottom rung was 9.56 A. At first I thought I made mistake when solving, but tried several times and with different methods always getting same results. Now, I think problem is with this software. If you can solve this manually or you have some kind of simulation software, please do it so we can compare results...

P.S. Merry Christmas to everyone who celebrate.

i was lazy to do it by hand but i tried SwitcherCadIII (free from www.linear.com) and first current is greater.
the RMS values i was getting are 7.9764A and 6.6887A, peak values are 11.3A and 9.3A.

pozdrav...

here is the screenshot (to integrate, keep Ctrl button pressed and then click on signal label of selected trace):

Simple circuit

I got the same thing you did using MultiSim Student lite V 10.0




This is what my results looked like.

I solved this long hand and made the upper current larger than the lower. By changing the sign on the lower voltage source you can flip the result so that the lower rung now has the greater current.

Is there any significance as to where the V2 is located on the diagrams for the simulation ? (i.e. can the V2 be located near the positive side of the voltage source)

panic mode said:

here is the screenshot (to integrate, keep Ctrl button pressed and then click on signal label of selected trace):

Click to expand...

Panic mode, I believe, your simulation showed different result because you use 120 V as maximum value (peak). 120 is RMS according to their simulations.
I think there is a problem how EWB (El. WorkBench) internally calculate these currents. It is not according my textbooks and this can be very misleading.
I noticed same thing first time I tried to work with EWB.

Really strange...

mikas_m said:

Panic mode, I believe, your simulation showed different result because you use 120 V as maximum value (peak). 120 is RMS according to their simulations.

Click to expand...

thank you,
you are absolutely correct...

Pandiani - can you plot the voltages at nodes 3 and 5 ?

Node 3 is the reference sine wave
Node 5 should be a sine wave at -120 degrees

Here it is...

I noticed this mismatched, when I was solving your problem with the 3 phase circuit. My calculations repetitously gave one result, while simulation other.

I hope this plot can be helpful.
http://www.plctalk.net/qanda/uploads/Plot.jpg

The voltage plots are shown correctly, but the currents are calculated as if V2's phase angle is +120 degrees.