[Amps] Step Start in General

[George K. Watson]

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, 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? I
have grown lazy and tend to model everything anymore.

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