[Amps] Step Start in General

[R.Measures]

>For the first two valve supplies that I built, I used a fairly conventional
>step start for the HV transformer primary and filament transformer primary.
>The circuits were processor controlled by a jStamp (www.systronix.com) and I
>used Crydom SS relays for the step.
>I am into another project at the moment and am considering using NTC
>thermistors from Ametherm for inrush current limiting. These seem
>appropriate and capable for the HV side, but I am wondering what the up/down
>side is, 

**  The down side is that they add ESR to the mains, which increases HV 
unregulation.

>and how to look at the design of the filament inrush limiting, as
>the timing of the inrush is substantially different from that of the HV
>side. Any thoughts? Anybody have a spice model for the filament behavior? 

**  A cold, thoriated tungsten filament has c. 8.3 x more Siemens of 
conductivity than a hot one.  


>I  have grown lazy and tend to model everything anymore.

**  I still like to measure things, of course.  
>
>BTW, the supply is for GS31/GS35B and will do about 2.8kv 2A CCS, the
>capacitors are 2x 40uF 5kV Oil for 80uF total. I have just finished framing
>the chassis for the transformer.
>
>George K. Watson
>K0IW
>
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