Thevenin equivalent of lattice network

[Mbert]

Homework Statement

Find the Thevenin equivalent network of the lattice network (see attached), viewed from points As and Br (terminals Bs and Ar are not connected to anything).

Homework Equations

The Attempt at a Solution

Without the resistance f, the problem is quite simple. I can find voltages at nodes Bs and Ar as a function of voltage between As and Br (potential dividers). Then insert f and check how it modifies the impedance? I think it only works to check the Thevenin impedance between Bs and Ar, not As and Br, but I'm not sure. Any help would be appreciated.

 

[gneill]

Sometimes redrawing the diagram can provide insight. Relocate the node B_s to the interior of triangle A_sA_rB_r and see what you get.

 

[Mbert]

I'm guessing I have to use the Y-D transformation, so I get 2 triangles in parallel?

 

[gneill]

I'm guessing I have to use the Y-D transformation, so I get 2 triangles in parallel?

There are several ways to continue, one of which is certainly to employ a Y-Δ transform.

You might want to note that resistor e runs directly between the "output" nodes, so it is in effect in parallel with all the rest. You could always remove it for now, figure out the resistance of the rest, then put e back in parallel to finish up.

 

[Mbert]

Yes, many thanks.