Re: Spacings Issue

Tue, 19 Dec 2000 14:39:30 +0000

 

Hello Ken,
 
First of all the "floating secondary ground" (if not connected directly to earth) should be treated as part of the secondary circuit which in many cases will require reinforced insulation to the primary circuit according to the working voltage measured.  Next, in most applications, the secondary circuitry can be cap coupled to earth ground and does not require basic insulation spacings for a primary circuit. I have seen equipment which incorporates TNV circuitry that does require supplemental insulation spacing at the primary working voltage from the TNV to earth due to Nordic Country deviations. I believe this is required due to poor earthing in these countries, and the thought is that if the safety earth was removed, reinforced insulation will remain between the primary circuitry and the TNV (basic + supplemental = reinforced). This is the information I had received in the past, but maybe some others in the group can provide you with more information.
 
Ed
 
>From: "Matsuda, Ken"
>Reply-To: "Matsuda, Ken"
>To: [email protected]
>Subject: Spacings Issue
>Date: Mon, 18 Dec 2000 18:37:22 -0500
>
>
>
>Hello Group,
>
>A circuit uses a floating ground in the secondary, and caps are used for
>protection from the secondary outputs to earth ground. The question is,
>under spacings requirements, would the secondary have to meet the high
>voltage requirements for spacings for primaries due to this earth ground.
>A few agencies have expressed desires to short the primary to secondary and
>require the the secondary to meet primary voltage spacings to this earth
>ground trace.
>
>Any help would be greatly appreciated. And thanks again for all your
>opinions
>
>
>
>Thanks,
>
>Ken Matsuda
>
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