Quick Thevenin Equiv Question

Swapnil · Feb 19, 2007

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

ranger · Feb 19, 2007

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 · Feb 19, 2007

ranger said: ↑

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 · Feb 19, 2007

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 · Feb 19, 2007

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 · Feb 20, 2007

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

doodle · Feb 20, 2007

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

rohinimovva · Feb 20, 2007

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]