
Signature
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarleRemoveThis@BOGUSsandia.gov
NOTE, delete texts: "RemoveThis" and "BOGUS" from email address to reply.
----- Original Message -----
From: "Chris Carlen" <crcarleRemoveThis@BOGUSsandia.gov>
Newsgroups: sci.electronics.cad
Sent: Tuesday, April 19, 2005 11:14 PM
Subject: [LTSPICE] Too many Teravolts!
> Greetings:
> Notice how this circuit causes some major voltage spikes to gazillions of
[quoted text clipped - 8 lines]
> Thanks.
> Good day!
Hello Chris,
I had a hard time with your circuit. I first tried with the
usual SPICE parameters, but this hasn't really helped.
After that I looked to your component values.
Lfilta: 25 Henry
Lfiltb: 25 Henry
L1: 250 Henry
C5: 4 Farad
What real word circuit contains an ideal 250H coil or
an ideal capacitor with 4 Farad?
Please add the following parasitics by clicking the right
mouse button over the appopriate component. A dialog will pop up.
Lfilta: Parallel Resistance: 1e7
Lfiltb: Parallel Resistance: 1e7
L1: Parallel Resistance: 1e7
C5: Serial Resistance: 0.01
The simulation will then run with the normal and the
Alternate solver. There are also no more "super spikes".
My learning from this:
Add a little bit loss to circuit elements if they
have such extreme values of ideal inductance and capacitance.
This helps to make it better solveable for any (LT-)SPICE engine.
Your real parts will have decades more loss than I
have added in your example.
Best regards,
Helmut
Jim Thompson - 22 Apr 2005 22:42 GMT
[snip]
>Hello Chris,
>I had a hard time with your circuit. I first tried with the
[quoted text clipped - 30 lines]
>Best regards,
>Helmut
I thought that fixing inductors was a built-in "feature" of LTspice
that Mikey cited repeatedly as one of the reasons that LTspice is
faster than PSpice?
...Jim Thompson
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Helmut Sennewald - 22 Apr 2005 23:52 GMT
> [snip]
>>
[quoted text clipped - 36 lines]
> that Mikey cited repeatedly as one of the reasons that LTspice is
> faster than PSpice?
Hello Jim
Yes there is damping(very small series resistance), but
it is very light. It can be overwritten of course.
Any automatic guess has to be very carefully choosen
so that it doesn't have impact on the the accuracy of
a simulation.
Best regards,
Helmut
Helmut Sennewald - 23 Apr 2005 00:30 GMT
>> [snip]
>>>
[quoted text clipped - 40 lines]
>
> Yes there is damping(very small series resistance), but
Sorry, it's a very very high parallel resistance.
> it is very light. It can be overwritten of course.
> Any automatic guess has to be very carefully choosen
[quoted text clipped - 3 lines]
> Best regards,
> Helmut
Endoscope - 22 Apr 2005 23:04 GMT
> ----- Original Message -----
> From: "Chris Carlen" <crcarleRemoveThis@BOGUSsandia.gov>
[quoted text clipped - 49 lines]
> Best regards,
> Helmut
Oh..... bum, perhaps you might mention this one to Mike. Mind you it's
probably not his problem but some Windows/News transfer snafu or somesuch.
There have been occasions when pasting text files into newsreaders where
some of the characters go wayward and when things get cut and pasted a bit
more something else happens..... the Greek u seems to be a favourite one.
Values get spumed on.
Yes, I've seen the teravolt/amp thing before, not just in LTspice. And if
I'm interested I start to mess about with series and parallel impedances to
try and tame them.
Spice, not that I know f.ck, finds an answer. If the answer satisfies the
question then it is right. Simple as that. Perhaps there is or should be
some way of setting up a box that says 'More than this amps/volts, bugger
off and try again'.
DNA
DNA
Chris Carlen - 26 Apr 2005 19:43 GMT
> Hello Chris,
> I had a hard time with your circuit. I first tried with the
[quoted text clipped - 9 lines]
> What real word circuit contains an ideal 250H coil or
> an ideal capacitor with 4 Farad?
Thanks for the reply!
Oh, I use 250H coils and 4F caps all the time. The surface mount ones.
Air core inductors and silver mica caps too. ;-)
Seriously, the component values are just bungled by the cut and paste.
This seems to happen a lot. The values should be 25uH, 250uH, 4uF.
> Please add the following parasitics by clicking the right
> mouse button over the appopriate component. A dialog will pop up.
[quoted text clipped - 11 lines]
> have such extreme values of ideal inductance and capacitance.
> This helps to make it better solveable for any (LT-)SPICE engine.
Yes.
Good day!

Signature
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarleRemoveThis@BOGUSsandia.gov
NOTE, delete texts: "RemoveThis" and "BOGUS" from email address to reply.