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# Re: [femm] Re: Current

- To: femm@yahoogroups.com
- Subject: Re: [femm] Re: Current
- From: David Meeker <dmeeker@ieee.org>
- Date: Mon, 22 Jul 2002 20:29:20 -0400
- References: <ahgh7h+q70o@eGroups.com>
- User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.0.0) Gecko/20020530

brian_hawes wrote:

> `Keith,
> Thanks for the reply. My problem is thus: I have a simple simulation
> of a single curent carrying ring. I have defined the current density
> in the model for the copper. If I simulate at very low frequency,
> such that skin and proximity effects are negligable, then the total
> current, found by using the block integral feature in FemView, is
> what I would expect - J x Area. Now, if I increase the frequency such
> that skin and proximity effects occurr, then the total current,
> measured with FemView appears to fall. I would expect, as you say,
> that the total current would remain constant, and just be
> redistributed.
> Brian
> `

If you define a "source current density," this is defines the current that you would get at 0 Hz. At nonzero frequencies, in conductive regions, some of the current gets bucked by inductance.
For your purposes, you want to apply currents via "circuit" properties, which are really constraints on the total current carried in a region. Then, the current redistributes itself due to eddy current effects, but the total amount of current is constrained to a certain value.
I've attached a zipped example of a 7-turn coil. Each turn has a "circuit" constraint applied to it so that each turn carries exactly 1 amp. The example is run a 10 kHz, so that there are some noticable skin and prox. effects.
Dave.
--
David Meeker

Attachment: `zip00030.zip`
Description: Zip compressed data

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