Get Help

Turn on suggestions

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

- Community
- :
- PTC Mathcad
- :
- PTC Mathcad
- :
- MathCAD exponential functions

Options

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

12-21-2020
03:28 PM

12-21-2020
03:28 PM

MathCAD exponential functions

Hi all,

I have a slight problem with my code.

I have highlighted and explained the flow as well as i can. Please let me know if further clarification is required. The .mcd file is also attached for your reference.

My question: When I look at the values of U_n and PTCU_n, the values seem to keep increasing indefinitely. In theory, PTCU_n should stabilize at 75% when tn_n reaches 6xRTC and not increase any further. I am not sure where I am going wrong.

Thoughts?

Any help is appreciated.

Thank you in advance!

2 REPLIES 2

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

12-21-2020
04:16 PM

12-21-2020
04:16 PM

Re: MathCAD exponential functions

Does this make sense?

I reduced the scale of PTCU by a factor of 100, to make it fit on the same scale as the others.

Note that your construct:

is reduced by me to

because the two surrounding expressions are not assigning anything.

Success!

Luc

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

12-21-2020
04:56 PM

12-21-2020
04:56 PM

Re: MathCAD exponential functions

Thanks for your response, Luc.

A clarification: The square waveform generator section is designed that way because I am modelling a motor inrush. Hence the two equations surrounding a<--a+1 are to define the spike in current during a motor start.

That aside, this certainly polishes my graph by a lot.

However, the exponential function (U_n) and thereby the PTCU_n function still does not settle at 75%. I am not sure why. With my hand calculation, the model yields the desired answer. But, with my code, it never seems to settle.

Do you think changing the exp to a log function might help?

Thank you, again!