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Re: [Amps] Step start

To: amps@contesting.com
Subject: Re: [Amps] Step start
From: Steve Thompson <g8gsq@eltac.co.uk>
Date: Tue, 05 Feb 2008 21:53:09 +0000
List-post: <mailto:amps@contesting.com>
> Hi All,
> 
> The purpose of a step-start is (mainly) to let the HV caps load smoothly.
> 
> The "classical" way to make a step-start is to short the resistor in the HV
> transformer primary with a relay switched after a delay made with an RC.
> This delay is mostly arbitrary put to 1 or 2 s.
> 
> Why not switch this relay with a divider from the HV voltage ? With the
> right divider, you ensure that the caps are really loaded and not supposed
> to be ?

As other replies show, people do it both ways - as have I. One 
thought relates to the (very rare) situation where there's a fault 
in the transformer or ht system that results in heavy current draw 
and low voltage so the step start doesn't switch out. The step 
start resistor can/will explode with the dissipation unless its 
huge (been there...). A fixed timer results in the mains fuse blowing.

To be fair, if you've a fault like that then a blown resistor is 
probably the last of your problems.

Steve
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