[Amps] 2500 uF at 450V DC

[Robert & Linda McGraw K4TAX]

As I recall (I'd have to look) my broadcast AM transmitter that I use on
160M and 75M uses only two 8 MFD @ 4500VDC oil filled caps for the HV
filters, choke input.  The plate voltage runs 3200 VDC and PA current is
some 480 ma but the modulators are also using the same supply which is
additional dynamic current demand.  (No, I don't run it in high power as it
is rated for a KW output and that's a wee bit illegal for ham use.)  I'd
guess that peak HV current totals upwards of an amp.  The excessive capacity
in a HV supply will spell disaster in the event of an arc or flashover.

As to HV wire, I've found that the Belden product is quite good, it's
flexible, and the big stuff is rated at 40KV.  The smaller "test lead" wire
is rated at some 5 KV as I recall.  I've rebuilt several old BC transmitters
using the larger product, thus replacing HV wire that was 40 to 50 years
old.

To that end, I have several pieces of very HV wire in 4 ft to 8 ft lengths.
These came from a 35KW UHF TV TX that ran some 40 KV DC at several amps for
beam current.  The stranded center conductor is #10 or #12 and is silver
plated.  The OD of the cable is some 1/2" to 5/8" and is nice and flexible.
I'd be glad to share some of it with you if you need really HV wire.

73
Bob, K4TAX

----- Original Message -----
From: "Norman Hockler" <norsan at bright.net>
To: <Amps at contesting.com>
Sent: Tuesday, July 01, 2003 11:24 PM
Subject: RE: [Amps] 2500 uF at 450V DC for $10.00 each


> All you need for plate filtering is about 20 uf or so.  Excess uf are
> discharge current you
> do not need.
>
> The statement that "Joules are good if you are converting them to RF."
> is not true when talking about tube flash over conditions (rockey point
> effect).
>
> As example ....  We need  1 amp of current to run our gadget and we are
using
> a car battery to supply the current.  The gadget works fine cause we have
> the 1 amp
> and the 12 volts... but our gadget shorts...we now have BIG amps to burn
> things up.
> The BIG amps is the same as the stored joules in the caps.
>
> The series resistor will help... BUT it is my opinion that a wire fuse is
> not fast
> enough to save you from damage.
>
> Will you blow things up every time.... probably not, but every time it
happens
> you stress components and then disaster.
>
> The less the uf  (joules of stored energy)  the less strain on components
> and therefor
> the less chance of damage if you get a flashover.
>
> Norm  N8NH
>
>
>
>
> At 08:11 AM 6/30/03 -0400, you wrote:
> >??
> >
> >Joules are good if you are converting them to RF.
> >
> >On 29 Jun 2003 at 17:43, Conrad Farlow wrote:
> >
> > > Put 10 in series and you have a whole lot of joules to deal with in
> > > the event of a flashover, bad idea IMO.
> > >
> > > Conrad G0RUZ
> > >
> > > FOR SALE:
> > >
> > > ELECTROLYTIC CAPACITORS
> > >
> > > 2500 uF at 450V new, top-grade caps.
> > > Cornell-Dubilier 400c series.
> > > 4" tall, 2" diameter.
> > >
> > > Put 10 in series and you have 250 uF at 4500V DC
> > > Put 20 in series and you have 125 uF at 9000V DC
> > >
> > > Pricing:
> > > QTY 20 or above at $10.00 each
> > > QTY 10 or above at $12.00 each
> > > QTY <10 at $15.00 each
> > >
> > > Shipping Additional
> > >
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