# solving RLC circuits

Discussion in 'General Electronics Chat' started by Nara Shikamaru, Apr 8, 2008.

1. ### Nara Shikamaru Thread Starter Active Member

Nov 24, 2007
92
3
hey everybody!!....sorry for the stupid question........Can you use Thevenin, Norton, superposition and Node analisys in RLC circuits???......if so....could you pass some examples circuits???......Thanks!!

2. ### hgmjr Moderator

Jan 28, 2005
9,030
214

Do you have an example RLC that you are attempting to solve with any of the mentioned circuit analysis methods?

hgmjr

3. ### Nara Shikamaru Thread Starter Active Member

Nov 24, 2007
92
3
not really, im kind of studying for real circuits solving and designing!! and in all textbooks it appears that RLC circuits just can be solved by Phasors, complex math and Laplace transform!!....

and i wanted to know if you could solve them by Thevenin, Norton, superposition or Node analysis!!!........i dont have a particular circuit!!.....i was wondering if you all have RLC Circuits solve by any of those methods!!....thanks!!

4. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Here is a link to the wikipedia section on RLC circuits. If you scroll down a bit you will see the application of KVL to analyze a series RLC circuit in the frequency domain.

hgmjr

5. ### scubasteve_911 Senior Member

Dec 27, 2007
1,202
1
The steps needed to fully understand a problem involving reactive components, initial conditions, or dependent sources need basic circuit theory coupled with a method to solve differential equations.

The simplest method is to learn to write your circuit in terms of the Laplace domain. Then, you apply your appropriate circuit theory to the problem and write equations. The next step, you "plug and play", as we call it, until the solution is found.

So, Laplace Circuit, circuit equation, isolate desired variable (current, voltage), inverse laplace for time domain solution.

Steve

6. ### Nara Shikamaru Thread Starter Active Member

Nov 24, 2007
92
3
for example.....i have this circuit i got from Industrial Electronics by Timothy Millman......can the components values be calculated using Nodal Analysis, or thevenin, or supersposition???..... would it be??.....what if i assume RL as a DC motor? (has some inductance and resistance).....so technically the circuit would have RLC components....

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7. ### scubasteve_911 Senior Member

Dec 27, 2007
1,202
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Circuit design is about understanding component value consequences by writing reasonable (assumptions might be needed) equations about a particular circuit, then understanding the direct relationship of these values. In many cases, you will have to set a lot of these values to particular ratios and using your judgement to come to a conclusion.

What you are directly asking cannot be solved via normal circuit analysis tools. Whenever you have a device, such as a transistor or FET, you need to do two separate calculations. First, you need to find a DC solution, which will give rough biasing conditions for the devices. Secondly, you will need to do an AC analysis, which is crucial for understanding how your circuit will react (poles, transient response, etc).

In a lot of circumstances, FETs or transistors are simply modeled in two states if they are meant for cutoff/saturation operation. This can greatly simplify your solution..

Steve

8. ### hgmjr Moderator

Jan 28, 2005
9,030
214
I see you have elected to cast a wider net from the RLC question mentioned in your initial post.

Scubasteve_911 is right. When you introduce components like the UJT and other similar active components you will need to replace them with a circuit model that uses conventional passive components along with dependent current sources and dependent voltages as appropriate to then make it possible to use conventional circuit analysis techniques.

hgmjr

9. ### Xolisa.X New Member

Apr 14, 2008
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YES brother......Remember when you are solving complex wave you r using superposition bcz when u r calculate your impedance you use one source at a time

10. ### baby_vL New Member

Mar 15, 2009
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in RLC series, do VL and VC have any relationship 2 each other...???? (blur blur blur)

11. ### Nara Shikamaru Thread Starter Active Member

Nov 24, 2007
92
3
Do you mean, VL (Voltage in Inductor) and VC (voltage in Capacitor)???.....if thats so....they dont have any relation....