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11-02-2013
02:32 AM

11-02-2013
02:32 AM

Circuit

Is it possible to solve this with odesolve or statespace?

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17 REPLIES 17

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11-02-2013
08:36 AM

11-02-2013
08:36 AM

Re: Circuit

And wat about it http://communities.ptc.com/message/222734

Start please and we will help if it need.

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11-05-2013
02:06 PM

11-05-2013
02:06 PM

Re: Circuit

Not sure of the initial condtions or if the equations are incorrect.

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11-05-2013
02:49 PM

11-05-2013
02:49 PM

Re: Circuit

Might be nice to explain what q1 and q2 are. If q is charge, there's only one charge holding device in your circuit.

And the amplitude of your 60 Hz? One? Really?

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11-06-2013
10:05 AM

11-06-2013
10:05 AM

Re: Circuit

I definitely doubt you initial conditions.

But apart from this - if you are searching for capacity voltage and currents, why don't you set up your equations in exactly that functions?

You didn't indicate where the switch you close at t=0 should be, so I assumed an uncharged capacity at t=0, but you can change that in the attached sheet.

You obtain the initial currents for t=0 from the system of equations considering that the capacity voltage for t=0 is a given (or precalculated) value.

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11-15-2013
06:25 PM

11-15-2013
06:25 PM

Re: Circuit

Couple years ago i have done something similar, please find attached. I deleted coments, thay were in russian.

I hope it will help You.

Regards

Andrii

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11-16-2013
10:16 AM

11-16-2013
10:16 AM

Re: Circuit

Andrii Luchko wrote:

I deleted coments, thay were in russian.

Why? Russian here is a second language after English.

And more.

It is a task for Prime with full units in matrix.

Sorry Prime points an error in your model:

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11-16-2013
11:36 AM

11-16-2013
11:36 AM

Re: Circuit

Its a fine thing to be able to use units here, otherwise the error would have been hard to spot. Wish we had that in MC15, too.

I'm too lazy to add the units but there seems to be a unit mismatch in the last but one line, too.

It looks like two expressions should be switched:

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11-16-2013
01:50 PM

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11-16-2013
02:04 PM

11-16-2013
02:04 PM

Re: Circuit

You are right. The two highlighted expressions are erranous but simply switching won't help. It seems that both expression have to be multiplied by a resistor to make the units fit.

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11-16-2013
02:34 PM

11-16-2013
02:34 PM

Re: Circuit

But in Mathcad 15 all is OK. See the attach!

Only for this I can use Prime (with M15)!

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11-16-2013
02:52 PM

11-16-2013
02:52 PM

Re: Circuit

!! Andrii's sheet seems to be OK including units !!

The error is your vector i of initial values. You assumed all to be Ampere, but the last two are voltages!

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11-16-2013
07:38 PM

11-16-2013
07:38 PM

Re: Circuit

Here is the modified sheet with the correct units.

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11-18-2013
12:18 PM

11-18-2013
12:18 PM

Re: Circuit

Originally I tried to estimate Partial Discharges in insulation, so I tried to get solution for as much as possible stiff system of equations. I used numerical and analytical solution. Attached another solution where used Jacobian matrix. Hopefully it will be useful for some body.

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11-18-2013
01:37 PM

11-18-2013
01:37 PM

Re: Circuit

Sorry, Andrey.

This problem is for Prime with units - ohm, A, V, H, F etc

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11-18-2013
03:11 PM

11-18-2013
03:11 PM

Re: Circuit

Valery Ochkov wrote:

Sorry, Andrey.

This problem is for Prime with units - ohm, A, V, H, F etc

So feel free to convert and add units if you think you need it

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11-18-2013
09:21 PM

11-18-2013
09:21 PM

Re: Circuit

Werner Exinger wrote:

Valery Ochkov wrote:

Sorry, Andrey.

This problem is for Prime with units - ohm, A, V, H, F etc

So feel free to convert and add units if you think you need it

Sorry not I need but we need.

Units can point us possible errors as in the first sheet

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11-19-2013
04:34 AM

11-19-2013
04:34 AM

Re: Circuit

Sorry not I need but we need.

Of course its good to be able to use units in solving DEs and I wish we could do so in MC15, too, but I won't consider it an urgent need. If someone creates and posts worksheets without units to a help a questioner he should not get the impression that his effort is disrespected just because he is not using units. Furthermore it makes sense to post a MC15 sheet as an answer and not a Prime one if he questioner is seen to use MC15 himself.

Units can point us possible errors as in the first sheet

Yes, sure, units are fine. But in the sheet you mention the error was just introduced by assigning the wrong units 🙂 Andrii's unitless MC15 sheet seems to was OK.