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Newbie

## Circuit

Is it possible to solve this with odesolve or statespace?

17 REPLIES 17

## Re: Circuit

Start please and we will help if it need.

## Re: Circuit

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

Sapphire III
(in response to ZW1)

## 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?

## 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.

## Re: Circuit

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

Regards

Andrii

## 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:

## 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:

## Re: Circuit

 Werner Exinger wrote:It looks like two expressions should be switched:

Sorry, no!

i/C and i/L has different dimensions.

## 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.

## Re: Circuit

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

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

## 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!

## Re: Circuit

Here is the modified sheet with the correct units.

## 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.

## Re: Circuit

Sorry, Andrey.

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

## 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

## Re: Circuit

 Werner Exinger wrote:Valery Ochkov wrote:Sorry, Andrey.This problem is for Prime with units - ohm, A, V, H, F etcSo 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

## 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.

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