Re: [Help-gnucap] pure inductance simulation

[al davis]

On Wednesday 30 June 2010, Josef Vukovic wrote:
> I have a question reagrdig my gnucap simulation of a pure
> inductance.
> 
> Here is my gnucap code:
> 
> Pure Inductance:
> 
> V 1 0 sin(0 220 50)
> L 1 0 100m ic=0V
> 
> .print tran v(1) i(L)
> 
> .tran .001 .02 >AcXl.dat uic
> .end
> 
> 
> When I plot the simulated data with gnuplot I get
> a Voltage leading current by 90 degrees, but the
> current is only positive and don't change to negative
> values. How can I simulate a pure inductance with gnucap?

The results are correct.

The input starts at zero.  For as long as it is positive, 
current will rise.  When the input goes negative, current will 
drop, and continue to drop as long as it is negative.  Since the 
wave is symmetric, this returns it to zero, so in this case the 
current will always be positive.

You can get negative current with a different starting point.  
Try setting ic=-10.   Note that for inductors, ic (initial 
condition) is current, even if you say "ic=0V".  The "V" is 
ignored.