Hi,

I am just writing code series rlc circuit like below.

module series_rlc(p,n);
inout p,n;
electrical p,n;
parameter r=1;
parameter l=1u;
parameter c=1u;
real vr;
real vl;
real vc;
analog
begin
V(p,n)<+r*I(p,n);
vr=r*I(p,n);
V(p,n)<+ l*ddt(I(p,n));
vl=(l*ddt(I(p,n)));
V(p,n)<+(1/c)*idt(I(p,n));
vc=(1/c)*idt(I(p,n));
end

But when I check vl in waves it is always showing zero.
I've two questions
1>why the values of vl is zero if I apply a dc or pulse voltage source with enough high and low pulse (around 10 us high and 10 us low on p)
2>what will this vr,vl,and vc values display will it give voltage across resistor,voltage across inductor,voltage across capacitor individually or something else.

This appears to be a valid implementation of a series RLC. There should be no topology errors if you drive it with a voltage source, nor should there be any concerns about the initial condition on the capacitor, though you can specify an initial condition if you like.

As to why vl is zero, it should not be if I(p,n) is changing. It is easy to check whether the results are correct. To do so, simply observe I(p,n), calculate the time derivative, multiply by l, and see it matches the value of vl.

-Ken

Try it without ultrasim.