Re: Coupling vs secondary voltage chart

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Antonio,

At 03:13 PM 6/18/2005, you wrote:
> Tesla list wrote:
> > Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
> > Hi Antonio,
> > The problem I ran into was knowing "NewVin" in the case of a primary 
> > current controlled DRSSTC.  In order to know NewVin, I would have to know 
> > NewIprimary ( Xo[4}(t+dt) ) which I will not have until the simulation 
> > cycle ends.  The NewVin is controlled by the primary current 
> > NewIpri.  When the cycle starts, I don't know what NewIpri will be.
> > So I set the NewVin equal to the LastVin.  This will cause Vin to 
> > actually switch one cycle later.  But that really is the case in a real 
> > DRSSTC since the electronics take time to switch.
>
> The problem is not in the calculation of Vin based on the last
> calculated current. I agree that this is a reasonable approach.
> The problem is that by always using Vin+Vin, at each transition
> a sum that should be zero goes to a full sum.
> Consider what this means, in a transition from -Vin to +Vin at t0+dt:
> Vin(t0)+Vin(t0+dt) should be 0. You are using 2*Vin, what is
> equivalent to say that Vin(t0+dt)=2*Vin.
> Continuing, Vin(t0+dt)+Vin(t0+2*dt)=2*Vin means that Vin(t0+2*dt)=0
> Continuing, Vin(t0+2*dt)+Vin(t0+3*dt)=2*Vin means that Vin(t0+3*dt)=2*Vin.
> The input voltage is then oscillating between 0 and 2*Vin at each step.
> The oscillation gets worse at each transition. This has little effect
> in the simulation, however, as the high-frequency component is rejected
> by the relatively narrowband circuit (and by the simulation method).
>
> Antonio Carlos M. de Queiroz

I see....  I applied a fix which I think will correct it.  I just used the 
old value of Vin from the last iteration.  This will actually be a dt late 
in time, but it probably switches more accurately this way and I think it 
fixes the oscillation problem.

............
        for (T1 = T1_start; T1 <= T1_stop; T1 = T1 + T1_inc)
{
  Vin_old = 0.0;
  if (X0[4] >= 0) Vin=Vrail; else Vin=-Vrail;   //Inputs Vin for DRSSTC case
  if (T1 > DwellTime) Vin = 0;                                  //Dwell 
time shutdown

      /* X1=X0+(dt/2)*[A]*X0+(dt/2)*B*(vin(t0)+vin(t0+dt)) */
      for (j=1; j<6; j++) {
        X1[j]=X0[j];
        for (k=1; k<6; k++) X1[j]+=(T1_inc/2)*(A[j][k]*X0[k]);
        X1[j]+=(T1_inc/2)*B[j]*(Vin_old+Vin);
..................

I made this change in the latest version and it changes the numbers a bit 
probably for the better ;-)

http://drsstc.com/~terrell/modeling/scantesla622.ZIP

This version also has the 10% to 90% streamer energy rise time calculated...

Cheers,

        Terry