[Amps] soft start, how to determine if needed?

[Edward Swynar]

Hi Guys,

FWIW, I had to re-build my rectifier stack at least twice before I finally
incorporated a soft-start / step-start scheme in the primary of my B+
transformer...

The p.s. is a full-wave rectifier job, applying 2.5 KV to a pair of 813s.

Since incorporating the scheme, I have had no further troubles in this
regard.

As someone said before me, it's "...cheap insurance", and not all that
daunting a task to add-in, even after the fact.."

~73~ de Eddy VE3CUI - VE3XZ


*******************************

----- Original Message -----
From: "Alex Eban" <alexeban at gmail.com>
To: <felipe at dxwatch.com>; <Amps at contesting.com>
Sent: Wednesday, February 24, 2010 3:39 AM
Subject: Re: [Amps] soft start, how to determine if needed?


> As far as possible, USE ONE!!!!!
> First, the cold resistance of a tube's filament is as low as one tenth of
> the warm filament, so inrush currents can reach 10 times the operating
> value.
> Second, inrush current of a HV power supply can reach a hundred amperes,
> measured with a Tektronix current probe. If nothing else, that current can
> weld the switch contacts!
> I don't have to tell you that the stresses on the rectifiers don't do any
> good and the capacitors are also badly stressed.
> Today, almost all integrated circuits intended for power supply control
> incorporate some form of soft start circuitry, precisely for reducing
these
> stresses.
> Use step start or soft start, it's very cheap insurance.
> Alex 4Z5KS
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Felipe Ceglia - PY1NB
> Sent: Tuesday, February 23, 2010 3:34 PM
> To: Amps at contesting.com
> Subject: [Amps] soft start, how to determine if needed?
>
> Hi folks,
>
> Regarding this recurring topic about soft starting...
>
> How can one determine if it is needed or not?
>
> Should HV be soft-started as well?
>
> What would be the best math to determine the soft-start dumping resistors?
>
> 73,
>
> Felipe - PY1NB
>
> --
> Felipe Ceglia - PY1NB
> --------------------------------------------------------------------------
--
> ---------
> PR1T team member /// Rio DX Group member /// Araucaria DX Group member
> http://www.dxwatch.com /// http://reversebeacon.net ///
> http://riodxgroup.dxwatch.com
>
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