undefined variable using find

[ptc-4578313]

Hi all

i found many discussions on this specific subject but.... I was not able to solve my problem.

I'm new with Mathcad and I'm afraid I'm doing something wrong.

Could someone please take a look at my xmcd?

Thanks

Giovanni

[wayne]

I think you are missing some initial conditions , Tv and Gama1

Check each side of the bollean expressions, they should all calculate to a value with the initial guesses.

For example, cut and past the RHS of Ik/Is, type= and you will see a unit problem with the cos()

[ptc-4578313]

Hi Wayne and thanks for your suggestion.

You were right (I missed some measureament units (like s or A). Now I checked all the equations and the initial guesses are working ( i'm able to see the initial value for the four equations).

Unfortunately this didn't solve the problem....I still get and undefined variable error

Thanks

Gio'

[RichardJ]

Gamma1 (LHS of last expression) is undefined.

[ptc-4578313]

Hi Richard,

thanks. I modified the code according to all your suggestions but it still doesn't work....

One question: could the initial guesses values be responsible? I tried also to change the Find function with the Minerr function ( that should return each solution even if is not very close) but I have the same problem...

Here attached the last version of the code

Thanks

[RichardJ]

Tv was undefined.

Also, somehow you got several occurrences of variables as constants. I changed the color of the constant style and highlighted the regions so you can see this.

If you change the styles from constants to variables then minerr will work. Find will not converge, but that might just be my guess value for Tv.

[ptc-4578313]

Hi Richard

thanks! You are right after changing to variables i was able to find a solution with minerr. i'll work on it and on the initial values to find a solution with "find"

Thanks

Giovanni

[AndyWesterman]

Hi,

Finally seen it!

Tv is only referenced in the Find(...) statement , it should be Tk.

Once you make this substitution Find is able to convrge to a solution.

I've added a few other changes before step 5 so I don't know if it will change the nature of the solve block equations.

I would be very interested in progress on this sheet as I have been trying to understand this type of resonant converter for a while.

It is a very difficult proposition as there seem to be far too many independant variables.

I'm obviously not looking at the problem from the correct angle

Regards

Andy

[ptc-4578313]

Hello Andy

sorry for my late reply.

Finally the code is working

Thanks everybody and let me know if you need some info on this LLC sheet. I'll be glad to share it with you

Bye

Giovanni