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Re: Filter Choke Design
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To: tesla-at-grendel.objinc-dot-com
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Subject: Re: Filter Choke Design
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From: mmccarty-at-dnaco-dot-net-at-dnaco-dot-net
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Date: Thu, 07 Mar 96 16:50:04 +0500
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>Received: from kirk.dnaco-dot-net (root-at-kirk.dnaco-dot-net [206.150.232.3]) by uucp-1.csn-dot-net (8.6.12/8.6.12) with ESMTP id PAA09541 for <tesla-at-grendel.objinc-dot-com>; Thu, 7 Mar 1996 15:35:35 -0700
> From: "Harri \"Haba\" Suomalainen" <haba-at-snakemail.hut.fi>
> To: tesla-at-grendel.objinc-dot-com
> Subject: Re: Filter Choke Design
> Why is nobody using the setup often seen in filters ie. wind two
> windings to the same core. Properly phased they will cancel each
> other out when one lead makes flus +B the other is making flux -B.
> The net will then be 0 naturally. Insulation problems will be a lot more
> severe to mention one problem. Coil on the other hand will get lot
> smaller.
This is referred to as a common mode choke. Common mode EMI occurs when
the RF sees the two wires as one conductor and travels down both using
ground to complete the circuit. This filter will remove the common mode
RF from the lines. The RF we are basically concerned with is the current
flowing from the Tank circuit on one wire, through the transformer, and back
to the tank circuit on the other wire. This is differential mode EMI and is
not effected by the filter you described because, as you stated, the fluxes
cancel each other having zero effect on the RF current.
-Mike McCarty