Why is My LTSpice Thevenin Resistance 7.6 Ohms?

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The discussion revolves around the calculation of Thevenin resistance in an LTSpice simulation, initially stated as 7.6 ohms but later corrected to 6.6 ohms due to a miscommunication about resistor values. The correct Thevenin resistance is derived from a 3-ohm resistor in series with the parallel combination of 9 ohms and 6 ohms. The voltage source used for measurement is 1 volt, resulting in a current of 151.51 mA, which confirms the 6.6-ohm resistance when calculated. Participants clarify the need for accurate circuit representation and netlist sharing for troubleshooting. The conversation highlights the importance of precise values and configurations in circuit simulations.
ntetlow
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Attached is an ltcpice net file.
The thevenin resistance betweed the 3ohm and 6ohm resistor is 7.6 ohms. This works out as 3ohms plus the parallel value of 20||6 (4.6ohms).
My problem is - Why is this the thevenin resistance, could someone please explain?
 

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ntetlow said:
Attached is an ltcpice net file.
The thevenin resistance betweed the 3ohm and 6ohm resistor is 7.6 ohms. This works out as 3ohms plus the parallel value of 20||6 (4.6ohms).
My problem is - Why is this the thevenin resistance, could someone please explain?
My LTSpice software is on a different computer from the one I'm working on right now. Can you post a couple of screenshots of your circuit and your simulation results?
 
Thanks for the reply. Screenshot attached.

Neil
Screenshot (7).png
 
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Sorry, just realised that i've sent a different version of the ltspice, instead of 20ohms as above, please read 9 ohms(2 +3+4) making the thevenin resistance 6.6ohms
 
What voltage is ##V_1##?
 
V1 is 1 volt. it is used to measure the thevenin resistance. the screenshot shows the current
The current is 151.51mA, dividing 1 by 151.51mA gives a resistance of 6.6 ohms.
 
ntetlow said:
Sorry, just realised that i've sent a different version of the ltspice, instead of 20ohms as above, please read 9 ohms(2 +3+4) making the thevenin resistance 6.6ohms
That looks correct (I've deleted a couple replies of mine just now that were wrong). The 3 Ohm resistor in the ##V_1## source leg is in series with the 9//6 Ohm resistances.
 
Attach the LTspice.asc file to a post by renaming it as LTspice.asc.txt
Rename it to LTspice.asc then run it as LTspice program. See attached.
If you post a netlist, we must paste it as a command, then we see a different layout to you.
thev3.png
 

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Yes, I see it now, just a matter of shifting things round, I wondered if that would do it.
Thanks for your help.

Neil
 
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