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Re: [Amps] Step start resistors, another solution

To: "Dudley Hurry" <>,"K7RDX" <>, <>
Subject: Re: [Amps] Step start resistors, another solution
From: "Paul Christensen, Esq." <>
Date: Mon, 5 Jan 2004 16:52:38 -0500
List-post: <>
> Another way to limit the surge is to use Crossing Relays.   I use two 40
> crossing relays on a 4000 volt/2 amp HV supply, and it works great.
> work by not completing the circuit until the amp draw would be zero during
> the 60 cycle phasing.

I've seen solid-state zero-crossing switches used for this purpose.
However, maximum current is achieved in just 90-degrees at 60 Hz (assuming
no zero reactance in the circuit).  This equates to only 4 ms.   It this
sufficiently enough time to limit filament current in-rush, especially with
directly-heated cathodes?

-Paul, W9AC

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