# Need help to find the mistake.

Discussion in 'Homework Help' started by interesting_dude, Oct 11, 2013.

1. ### interesting_dude Thread Starter New Member

Jul 28, 2013
20
0
Hello everybody!

I need a help to understand where is the mistake in my SPICE (programm: SPICE 2G.6) netlist. I have drawn an average-complexity (as for me) AC a circuit to test myself, and calculated everything what I have learned (except power), every property (voltages, currents, and their angles), but those values seems to be incorrect. However, when I check my circuit with EWB (programm: Electronics Workbench Version 5.12), it says me that everything is okay. But SPICE tells me that I am completely wrong!

Some images are too big for this forum, so I will paste links to them.

Here is my drawn circuit with netlist:

http://i42.tinypic.com/2i1cc29.jpg

Here are my attempts to solve the circuit (most calculation were made on scientific calculator, so no need simple formulas):

http://i41.tinypic.com/33a3slu.jpg

http://i40.tinypic.com/33uaekn.jpg

Here is the netlist:

Here is what SPICE tells me:

And here are the EWB results for currents only, and that is enough for me for thinking that I am on the right way:

What do you think?

2. ### WBahn Moderator

Mar 31, 2012
22,869
6,831
I haven't done AC analyses in any SPICE for many years, so I could be wrong on this, but doesn't the .AC analysis generate an impulse response of the circuit in the frequency domain? Your EWB results look like steady state results in the time domain.

Hopefully that at least gives you someplace to explore.

3. ### LvW Active Member

Jun 13, 2013
674
100
* AC analysis of a circuit using the SPICE code is performed NOT via an impulse response. It is based on classical calculations in the frequency domain.
* There is no ground reference in the shown circuit diagram.

4. ### WBahn Moderator

Mar 31, 2012
22,869
6,831
Note that I'm only saying what it generates, not how it generates it. I believe that what it generates is the impulse response in the frequency domain, often called the transfer function.

5. ### interesting_dude Thread Starter New Member

Jul 28, 2013
20
0
Impulse response? Transfer function? Frequency domain? Time domain? May God has mercy!!! Will these words appear in the future chapters of e-book?!

Look, I have just added ground to the circuit — nothing have changed.

I realised that I had done few analyses on the such AC circuits before, and hand-writed results always matched with results of two programms. Now only with one.

6. ### LvW Active Member

Jun 13, 2013
674
100
In your netlist I see a part called L1 that does not appear in the diagram.

7. ### interesting_dude Thread Starter New Member

Jul 28, 2013
20
0
No, I think it is in place.

8. ### LvW Active Member

Jun 13, 2013
674
100
Sorry, my mistake. Im was blind.

9. ### Jony130 AAC Fanatic!

Feb 17, 2009
4,461
1,262
I do a I quick calculation check of your and this is what I find

Ztot = XL1 + ((Xc1 + R1)*(XL2 + R2))/((Xc1 + R1) + (XL2 + R2)) = 899.226 + j98.4753

Ztot = 904.602Ω

and

Itot = 24V/904.602Ω = 0.026531A = 26.531mA

And
Ic1 = 0.00247957A = 2.47957mA
IL2 = 0.0263132A = 26.3132A

10. ### interesting_dude Thread Starter New Member

Jul 28, 2013
20
0
I think some mystery hiding inside this program when analyzing my circuit. I am very concerned that it does not give me the true results. Now as before I should always rely on my own calculations.
I solved the circuit successfully  isn't that a holiday?!
Thanks for all for taking a part in this discussion!