Equations for three inductors connected together

AI Thread Summary
The discussion focuses on deriving state equations for a system of three inductors connected at a common point, with independent voltage sources at their unconnected ends. The goal is to eliminate the intermediary variable VT and express the dynamics of the currents in terms of the input voltages V1, V2, and V3. Participants highlight the importance of applying Kirchhoff's Current Law, which states that the current through one inductor (I1) equals the sum of the currents through the other two (I2 and I3). The original poster successfully integrates this law to eliminate VT and reformulate the equations accordingly. Ultimately, the problem is resolved by correctly applying circuit laws to achieve the desired state space form.
anon6912
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I have a system with three inductors connected together at a common point.
The unconnected ends of each inductor is connected to an independent voltage source.

Basically I want to get three expressions for the dynamics of the currents with V1, V2 and V3 as inputs.
i.e. i need to eliminate the intermediary variable VT.

I want to write the state equations for the system in the following format (state space form):
dSvnAJf.jpg


The system and, how far i got is below:
tQ4QVt2.jpg


I don't know how to proceed from here.
Or is it impossible to get it into the format I want?
 

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anon6912 said:
i.e. i need to eliminate the intermediary variable VT.

anon6912 said:
The system and, how far i got is below:
tq4qvt2-jpg.jpg

Here you removed ##V_{T}## from all the equations. You have di/dt (for 1, 2 and 3) in terms of V1,V2... etc without ##VT##.

Maybe I didn't understand your question correctly.
 

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You are missing an equation. Using the sign conventions from your drawing, i1=i2+i3. That is Kirchoff's Current Law.
 
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Phylosopher said:
Here you removed ##V_{T}## from all the equations. You have di/dt (for 1, 2 and 3) in terms of V1,V2... etc without ##VT##.

Maybe I didn't understand your question correctly.

At the time I was asking this question I don't think I had grasped the question correctly even myself.

What I initially wanted was to eliminate V_T.
But as a consequence of doing this I found out I had to/ could write I_1 in terms of I2 and I3.
I wasn't sure if this second part of replacing I1 with !2 and I3 was correct because I felt like it would eliminate a state from the system if I did that.
But I think it is correct and can be done.

So now I have a system with VT eliminated and the equations written in terms of V1 V2 V3 and I1 and I2 :)
 
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anorlunda said:
You are missing an equation. Using the sign conventions from your drawing, i1=i2+i3. That is Kirchoff's Current Law.
Thanks. I ended up integrating kirchhoff law and it worked :)
 
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