Re: [RFI] Wiring practices to minimize emissions

["Roger (K8RI)" <k8ri@rogerhalstead.com>]

We used twisted pair for a lot more power than that.
When we hipotted the HV lines (OD close to two inches, it'd take 15 
minutes to a half hour for the charge to equalize. That was prior to 87 
so my memory is a bit hazy.
73

Roger (K8RI)

On 7/13/2016 Wednesday 10:27 AM, nm8rmedic via RFI wrote:
> Gentlemen,
>
> Thank you for well considered input.
>
> 1) Mention was made of using twisted pair. Is that practical for 40 horsepower 
> motors?
>
> 2) I recall from past board discussions the necessity of minimizing the 
> distance between, and area encompassed by, power carrying conductors to reduce 
> emissions.  Would someone please expound on that.
>
> 3) The motor controllers will be soft-starts rather than VFD's . Are there any 
> special EMI considerations regarding soft-starts?
>
> Thank you,
> Scott
>
>
> Sent via the Samsung Galaxy Note® II, an AT&T 4G LTE smartphone
>
> <div>-------- Original message --------</div><div>From: Jim Brown <jim@audiosystemsgroup.com> 
> </div><div>Date:07/12/2016  8:34 PM  (GMT-05:00) </div><div>To: rfi@contesting.com </div><div>Subject: Re: [RFI] 
> Wiring practices to minimize emissions </div><div>
> </div>On Tue,7/12/2016 11:13 AM, James Gordon Beattie, Jr. wrote:
> > im, et al,
> > Breaking DC paths with optical interfaces reduces inductive and
> > radiated emissions.
> How do you use an optical interface in a circuit carrying 30A DC? Or
> even 30A AC?
>
> > Further, twisted pairs are good, shielded twisted pairs properly
> > bonded and grounded are better.
> That is NOT universally true. It depends greatly on shield construction.
> If the shield is a robust copper braid, it can improve isolation. If,
> however, the shield is foil with a drain wire twisted at the same rate
> as the signal pair and closer to one of the signal conductors than the
> other, the shield CAUSES differential-to-common mode conversion, which
> causes the cable shield to radiate the differential signal.  Nearly all
> currently manufactured "rack" cable has this defect, including those
> made by Belden.
>
> See Neil Muncy's landmark paper in JAES, June 1995. The essence of his
> work is on my website, and I've contributed several papers of my own
> extending his work.
>
> 73, Jim K9YC
>
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