[Amps] Step start

[Patrick Egloff]

Hello Mike,

Are'nt those beasts a little bit too resistive under normal operating
conditions and temperature ??
According to the datas found on the page you provided, the lowest value is
0.5 Ohm, which is enough to produce a significant voltage drop with the
current we use in our amps !

What reference did you use in your amplifier and did you place this limiters
in the transformer primary ?

73s (not limitied),
Patrick


2008/2/7, aborg <a_borg at yahoo.com>:
>
> I guess I'll chime in with my limited input. Why not
> use  simple "Inrush Current Limter thermistors ? I use
> them for my 4-1000A amp and my 7.5Kv power supply.
> Very simple to install and ver efficient. Purchased
> from Digi-Key,Mouser or even RF Parts.
>
> http://www.ametherm.com/Inrush_Current/welcome.html
>
> *****************************************************
> --- Ian White GM3SEK <gm3sek at ifwtech.co.uk> wrote:
>
> > Han Higasa wrote:
> > >GM all
> > >
> > >As Steve told whatever loop (open or closed) has
> > been chosen
> > >a situation where a relay contact will not close
> > and inrush-current
> > >limitation resistor R will never be shorten can
> > happen.
> > >
> > >To address this a "step-start duration" timer
> > should be added;
> > >and to monitor this a "step start duration timer"
> > timer should also be?
> > >
> > >Instead, robust R and an operator can do this by
> > perceiving
> > >"it takes too long and the step-start never lasts"
> > >
> > >I am using a 30-ohm 100-W resistor for the R now.
> > >I think I should disconnect my step-start delay
> > timer and measure
> > >the voltage across R in time elapsed, to make sure
> > the R will not
> > >barn out.
> > >
> >
> > A much simpler solution is a slow-blow (T) fuse in
> > series with the
> > current limiting resistor. This idea has been used
> > by Alpha and others
> > for many years.
> >
> > The fuse rating can be about 25% of the long-term
> > short circuit current,
> > eg for 230V and 30 ohms it could be a 2AT fuse. If
> > the normal step time
> > is less than about 1 second, this fuse will never
> > blow unless the
> > step-start "hangs". The step-start resistor must be
> > capable of handling
> > the "hang" current (the steady value when the
> > resistor is tuck
> > permanently between the mains and the amplifier) for
> > the several seconds
> > that it takes to blow the fuse, but it doesn't need
> > to be rated to
> > survive forever - the fuse will protect it.
> >
> > Incidentally, most step-starts are much longer than
> > they need to be, as
> > the big current pulses only occur during the first
> > few cycles of the
> > mains. The aim should be to make the first and
> > second current surges of
> > equal size, so that neither one is "worse" than the
> > other. A very long
> > step time doesn't really help with this - it doesn't
> > affect the size of
> > the first current surge, and doesn't do much to
> > reduce the second
> > current surge, but it puts much more stress on the
> > resistor.
> >
> >
> > --
> >
> > 73 from Ian GM3SEK
> > http://www.ifwtech.co.uk/g3sek
> > _______________________________________________
> > Amps mailing list
> > Amps at contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
>
>
> Mike-KK4MS
> a_borg at yahoo.com
>
>
>
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-- 
Patrick Egloff - TK5EP
email : pegloff at gmail.com
Fax : +33 826 698 954
Web page : http://tk5ep.free.fr