Quick Thevenin Equiv Question

[Swapnil]

Main Question or Discussion Point

What is the most general method that can be used to get the Thevenin equivalent for a circuit (one that always works)?

 

[ranger]

Always works? I've yet to see a situation where the general methods dont apply.
1)Remove the load.
2)Find the open circuit voltage across terminals AB (Vth)
3)Find the resistance looking in from the terminals (Rth) by shorting the voltage source or replace a current source with an open circuit.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/thevenin.html

 

[Swapnil]

3)Find the resistance looking in from the terminals (Rth) by shorting the voltage source or replace a current source with an open circuit.

What if you had dependent sources in that circuit? How would you find the resistance looking into the terminals? You can't short/open circuit dependent sources.

 

[doodle]

3. Deactivate all independent sources. Insert a voltage source Vs between AB and measure the resultant current I; then RTh = Vs/I. Alternatively, insert a current source Is between AB and the resultant voltage V is measured; RTh = V/Is. You may choose any nonzero values for Vs and Is, e.g. Vs = 1V and Is = 1A.

 

[ranger]

Ah, yes. I see your point. Well it turns out that what you for the independent source circuit cannot work for with only dependent sources.

http://en.wikibooks.org/wiki/Electronics/Thevenin/Norton_Equivalents#Thevenin_Equivalents

 

[Swapnil]

So is there a general method? What about test voltage/current source method? Does that method work for all types of circuits?

 

[doodle]

Yes, the method is applicable on all type of circuits.

 

[rohinimovva]

Hi U can visit www.powerelectrical.blogspot.com to see about Thevenin's theorem and more topics in theorems. Also to get clear idea when dependent sources present visit ths link
www.eas.asu.edu/~holbert/ece201/ECE201Lect-13.ppt[/URL]