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Re: [Amps] Step start resistors, another solution

To: amps@contesting.com
Subject: Re: [Amps] Step start resistors, another solution
From: Alek Petkovic <vk6apk@eon.net.au>
Date: Tue, 06 Jan 2004 06:06:13 +0800
List-post: <mailto:amps@contesting.com>
And Emtron use a thyristor slow start circuit in all their amps. I have not seen any circuits of this but it couldn't be too difficult.

It sure works better than anything else I've ever seen. Soft, silent and very effective.

73, Alek
VK6APK

At 04:52 PM 5/01/2004 -0500, Paul Christensen, Esq. wrote:
> Another way to limit the surge is to use Crossing Relays.   I use two 40
amp
> crossing relays on a 4000 volt/2 amp HV supply, and it works great.
These
> 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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