[Amps] Step start resistors, another solution

[PAUL HEWITT]

I've been using SSR's for several years now for various HV supplies.  The
zero crossing "turn on" feature is not enough by itself to limit inrush in
the larger supplies.  Without step-start my 80# 4KV supply will still "hop"
on the bench at turn on as well as dim the lights.  The bench outlet is a 15
foot run of #6 to the panel which is supplied by a 50 foot drop to the
transformer.  I use a second SSR to short a step-start resistor after
500-1000ms, completely quite.  Using a SSR for each 240v line never made any
sense to me as the SSR's built in snubbers always leak some current and
there is never an absolute DPDT "disconnect" from the line, (without pulling
the plug).  The SSR's also need a minimum current demand to stay "on" which
sometimes is not met during stand-by with large value equalizing/bleeder
resistors.  The result is cycling from on to off to on........ hummm!!!!
The best thing about the SSR's, I've never welded one closed!!
Cheers, Paul

PAUL HEWITT
WD7S PRODUCTIONS
QRO HOMEBREW COMPONENTS
http://wd7s.home.att.net


> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
> Behalf Of Dudley Hurry
> Sent: Monday, January 05, 2004 1:44 PM
> To: K7RDX; amps at contesting.com
> Subject: Re: [Amps] Step start resistors, another solution
>
>
> 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..
>
> Thanks and 73's,
> Dudley
> WA5QPZ
> jhurry at austin.rr.com
>
>
>
>
> ----- Original Message -----
> From: "K7RDX" <k7rdx at earthlink.net>
> To: "Ian White, G3SEK" <g3sek at ifwtech.co.uk>; <amps at contesting.com>
> Sent: Monday, January 05, 2004 3:12 PM
> Subject: Re: [Amps] Step start resistors
>
>
> > Most ops here in the good ol USA don`t have a problem with house lights
> > diming when powering up our amps....We usually run the psu from a
> dedicated
> > 240vac line....At least that`s my way here in Central WA....Also we have
> the
> > cheapest hydro power in the world!  We sell a lot of our  power to the
> boys
> > in Southern Ca.....Costs them a bit more than us. Incidentally, I step
> start
> > my 4kv supply with 25 ohms/200watt, and the 6700 supply with
> 50ohms/200watt
> > res. Been doing that for long time now and so far no bitching
> from either
> > supply...Good new year to all, Jim.
> > ----- Original Message -----
> > From: "Ian White, G3SEK" <G3SEK at ifwtech.co.uk>
> > To: <amps at contesting.com>
> > Sent: Monday, January 05, 2004 9:07 AM
> > Subject: Re: [Amps] Step start resistors
> >
> >
> > > >>
> > > >>Any ideas on what values to use for step start resistors?
> In the past,
> > I've
> > > >>tended to choose a value from the available stock -
> something like 50
> > ohms,
> > > >>100 watts, which limits the surge current to just over 4 amps. I
> expect
> > > >>that a value such that the current won't exceed the full
> load primary
> > > >>current of the transformer is probably best, but any suggestions?
> > > >>
> > > >>(I'll probably still use what's available in my stock of vitreous
> > enamelled
> > > >>wirewound resistors about 10 inches long and an 1 inch in diameter,
> > > >>though!)
> > > >>
> > > >>73
> > > >>
> > > >>Peter G3RZP
> > >
>
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