|Created||September 06, 2013|
|Last modified||September 06, 2013|
Demonstrating Thevenin and Norton equivalence and a way to show open circuit voltage, short circuit current and calculate the Thevenin and Norton equivalent resistances.
Demonstrating Thevenin and Norton equivalence and a way to calculate open circuit voltage, short circuit current and calculate the Thevenin and Norton equivalent resistances.
SWthevenin with Csamphold_thev and SWnorton with Csamphold_nort sample and hold the open circuit voltages of the two sources.
The two ammeters measure the short circuit currents when the two switches change state at T=1s.
Plot expressions are then used to calculate the open circuit voltages divided by the short ammeter currents.
After T=1, these expressions show the Thevenin and Norton equivalent resistances respectively.
However, there are some problems with this simple simulation.
i) The equivalent resistance calculation should explode to infinity for T<1 because the ammeter currents are zero!
ii) CL does not show the calculated restances correctly for T<1, so in fact the plots look sort of OK although they are incorrect for T<1
iii) CL shows a nosensical slope on the resistance plots even though all values are 1.000.
Start Time = 1.1( i.e. after the switches change state)
is a way round this problem although CL still does not
show the T<1 behaviour correctly.
Simulate > Time Domain > Run Time-Domain Simulation
A correctly working LTspice version of this simulation:
can be downloaded from:
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