The question asks to find $$I_s \space\space and \space\space I_x$$
However, before doing so, I should simplify the circuit. Is my simplification correct?
(I.e. is tripling the value of I_s and removing these parallel voltage sources is equivalent to the original circuit?)
Also, is removing all these current sources, and putting 1 current source with 5 A equivalent to the original circuit?
(I could not check these using the simulator, as LTspice does not allow parallel voltage sources or series current sources).
I can find I_s and I_x if the simplification is correct, so is it?
Best Answer
You can get around this by using very small series resistors for the parallel voltage sources (or
Rserparameter). For series current sources (which you don't have in your specific example), you can do something similar by adding very large parallel resistors.Let's try it out. We'll use resistances which are small relative to the other resistors in the circuit. Since we're in the single to tens of ohms range, I picked 1µΩ. If you had resistors in the hundreds/thousands of ohms, I might've selected 1mΩ instead. Anyway, you don't want to put these on all the voltage sources, but just one per parallel branch like shown below. Note: V6 was added as a way to measure the current in that branch.
Now, let's do your simplification and re-run the simulation.
2.654A is almost exactly 3x 885mA, so I say that checks out.
Let's try this simplification and see if I(V1) and I(V6) stay the same.
Looks good to me!
One last thing to note is that LTspice measures current through voltage sources from the [+] side to the [-] side. So the answers here might be negated from what you got on your hand calculations.