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Re: [Amps] Choke input filters, design criteria?

To: Amps <amps@contesting.com>
Subject: Re: [Amps] Choke input filters, design criteria?
From: Chris Wilson <chris@chriswilson.tv>
Reply-to: Chris Wilson <chris@chriswilson.tv>
Date: Wed, 19 Dec 2012 14:14:03 +0000
List-post: <amps@contesting.com">mailto:amps@contesting.com>

> 4 H is a bit low; 8 would be better.  Choke input filters are good for
> power supply loads that are fairly constant, i.e. modes like AM, FM,
> and RTTY.  Take a look at the designs used in earlier amps like the
> Heathkit HA-10 as something to work off of, also the power supply
> sections of 1 KW vacuum tube AM broadcast rigs.  Don't forget old
> handbooks, West Coast and ARRL from the '40s and '50s.  if you are in
> the UK perhaps RSGB has old handbooks with design criteria.  You could
> start with an 8 uF oil cap.  Let's assume you are going with 3.5 KV.
> Look for a cap rated for over 4; 4.5 KV or more is a good idea.
> Follow that with the choke and another oil cap like the first one at
> the input.  Don't fool around with electrolytics that will need to be
> replaced some day--this is a filter that will last as long as you do.
> Use the ratings of the choke as your guide.  Make sure the v. rating
> of the caps is working volts DC.  Stay away from energy discharge
> caps--a genuine filter cap will be bigger with sizable insulators on
> the contact lugs.

> 73
> Rob
> K5UJ




19/12/2012 14:03

Thanks for the reply Rob. Is there a way to check the inductance of
another choke I have? The other one is bigger, and is from a 3 phase
supply for a Henry RF Generator. It gave just under 5kV at 1.5 amps.
Henry use the same part number in both the 3 and single phase versions
of the HV supply, but the single phase version uses 2 off 0.1uF
resonating capacitors, and a 4uF filter cap, with fairly low value
bleeder resistors. I believe these are to keep off load voltage in
check? The Henry schematics show both supplies using the same part
number of choke, but the 3 phase uses no resonance caps. The
schematics don't give the inductance though.

I believe an HV choke needs measuring for inductance with DC on it,
for the purposes of use as a resonant choke, and making it resonant at
twice the mains frequency (100Hz in this case, after a full wave
bridge).



-- 
       Best Regards,
                   Chris Wilson.

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