Re: Using MicroSim

Hi Daniel,

At 07:21 PM 8/3/99 -0400, you wrote:
>I just spent the last hour or so playing around with Terry's MicroSim files 
>(thanks for directing me to those Terry) and I think I've learned a lot. 

Great!!  Once you get started, it all falls into place pretty well.

>also have a lot of questions about what I've been seeing. First off I thought 
>it was brilliant how the various components were put together to simulate 
>what a real coil would do, however I'm not sure I know what all of these 
>parts are. 

Yes, I am brilliant aren't I!  :-)))  Actually, I and others have been
working on this basic model for about 1 1/2 years now...  As more is
learned, it just keeps growing and getting more sophisticated.  Actual
measurement are used to be sure the models simulate the real thing (that is
VERY important!).  Although I have programs that can predict many of these
element values,  Practically all of the values in my model are from actual
measurements.  The resistances in series with Cself and Ct are measured
using my brand new HP34401 meter.  I don't think anyone has ever really
considered or measured these before...  I should point out that many of my
models use a sync gap.  Gary Lau has a wonderful non-sync static gap
element model too that I think is in some of my earlier files at the site.
This is probably closer to what most people use.

You want to also see:


This is a paper about actual and modeled TC waveforms...

>Can someone explain to me what a MOV is and what it does? 

MOV = Metal Oxide Varistor = This is much like a zener diode.  When the
voltage reaches a certain level, it will momentarily short and protect the
rest of the circuit from over voltage.  They can take tremendous current
hits.  I use them to protect against secondary strikes.  My coil should be
able to get hit anywhere with out doing any damage.  So far, this has been
pretty well tested!!  The models shows these but those are just lines.  The
MOVs in the model have no function at all.  They just remind me they are
there in real life...  I really like MOVs and use them all over my TC.  The
only thing that has ever damaged them is the operator turning the variac up
way too high :-))

>Also by 
>plotting several of the probe things next to each other I noticed that the 
>sine wave of the starting AC voltage is exactly opposite of the wave coming 
>out of the transformer, can anyone explain this to me? 

Just put a negative sign in front of one of the waveforms.  This is just
like hooking the meter up backwards.  The computer simply takes the voltage
at point A and subtracts it from point B.  If it looks backwards, you can
simply make it take the voltage at point B and subtract it from point A...

>I'm not sure I 
>understand how the primary coil of the TC was simulated in these schematics 
>either, I see that the secondary coil was simulated with capacitors and 
>resistors (with values no doubt obtained through wintesla or something 
>similar) but I don't understand how the primary coil fits in, how are things 
>like turn spacing and wire width taken into account? 

The primary is simply taken as the input winding of a transformer with low
(0.145) coupling.  The value of the primary is around 132uH just like my
real coil.  There is a resistor there (Rpri) that is dependant on the coil
diameter and such.  All of the value shown are from actual measurements of
my coil.  I assume the primary is a very straight forward inductor, unlike
the secondary...

>Perhaps these are 
>prefigured and then the values plugged in with parts that can approximate a 
>primary, if so which parts should I be looking for? And how would I put a 
>probe onto the primary and one on the secondary to compare these waves? 

There is a very simple way to see any voltage or current waveform you want.
 In the icons, there are two symbols that look like arrows with a "V" and
"I" on their tops.  These are voltage and current probes.  Click on one and
place the probe symbol anywhere you wish.  When the simulation runs, it
will show this waveform.  It will show it right away if it has already run.
 You may want to go ahead and play with all the available toys in the menus
just to know that they are there...  90% of them are never used or changed...

BTW - There are two 4Meg *.pdf files that have some instructions to
MicroSim.  Although it is far better just to learn about it by playing with
it, the real instructions can come in very handy if your get stuck or have
to change some odd parameter.  The files are at the Orcad site or I can ZIP
them up and e-mail them to you also...

>assume they would be the same but I'd like to see it anyway out of curiosity. 
>Any other suggestions as to what I should try messing with next in these 
>programs would be appreciated, I think MicroSim deffinately has potential but 
>it'll probably take me awhile to find it all, until then I'm off to go play 
>with it some more :)

I will take awhile to get really used to it.  However, it is so
fascinating, that you will easily spend the time with it.

I am trying to refine the gap to be a bit more realistic and give a true
linear decrement and zero crossing spikes that match real measurements.
Also I would like to add some more basic elements to the gap that would be
useful in gap design and judging gap types...  Nothing so far.. but These
things take time...  I seems to be like back to back zener diodes with some
Ls an Cs and perhaps some resistance...

Very glad you got going so well!  



>Left, left, I hadda good brain but it left...