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Cornel19-Tanzanite
19-Tanzanite
April 29, 2024
Solved

Why solve cannot solve this system of diff eq with 3 eq?

  • April 29, 2024
  • 1 reply
  • 1829 views

Hi,

I am making something wrong? Are only 3 differential equations...

Cornel_0-1714392318215.png


But using laplace command this system of differential eq can be solved:

Cornel_1-1714392350034.png

 

See MCP9 file attached.

Best answer by Werner_E

It may be because of the dependency of the three function in equation #2

 

This works (derivatives of vc1 equals derivative of vc3:

Werner_E_0-1714393522028.png

 

v.C3(0) cannot be chosen freely!

Werner_E_1-1714393620951.png

 

 

1 reply

W
Werner_E25-Diamond IAnswer
25-Diamond I
April 29, 2024

It may be because of the dependency of the three function in equation #2

 

This works (derivatives of vc1 equals derivative of vc3:

Werner_E_0-1714393522028.png

 

v.C3(0) cannot be chosen freely!

Werner_E_1-1714393620951.png

 

 

    C
    Cornel19-TanzaniteAuthor
    19-Tanzanite
    April 29, 2024

    This is the circuit:
    @ttokoro 

    Cornel_0-1714394218397.png

     

    L
    LucMeekes23-Emerald IV
    23-Emerald IV
    April 29, 2024

    The situation of your circuit is impossible.

    To the left of the switch, at t=-0 you have a capacitor C3 charged to 5.7 V, in parallel to the series connection of a diode, that you model with a (constant) voltage source of 0.6 V, and a capacitor C1.

    This means that the voltage across C1 must be 5.7-0.6=5.1 V, not the 0 V that you set it.

     

    Success!
    Luc

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