[Amps] Henry 2k-4 HV inductor

[Jim Thomson]

Date: Wed, 13 Dec 2017 21:16:22 -0500
From: Ron Youvan <ka4inm at gmail.com>
To: amps <amps at contesting.com>
Subject: Re: [Amps] Henry 2k-4 HV inductor

<   On 12/13/2017 01:15 PM, Jim Thomson wrote:

  /* snip */
> ##  Although the  tuned choke concept works, it really is a throwback to the 
> 1950s.  IF the choke and parallel resonating cap just happen to resonate at 120 hz, 
> the peak V across that parallel tuned choke will skyrocket, and both the cap and choke 
> will explode.   Typ the choke is resonated just a bit higher than 120 hz, like 123 to 124 hz. 
> When u start sucking loads of plate current, the inductance of the choke will DECREASE a bit, 
> and the resonance of the choke + resonating cap combo will  INCREASE  some more, like now 
> up to 124-130 hz.
  /* snip */

  < I must have been taught all wrong, I was taught the capacitor (to
<ground) is in series with the series inductor forming a series resonant
<circuit that conducts the 120 Hz to ground, instead of storing energy
<like the "brute force" large capacitor. (bank)
-- 
  < Ron  KA4INM -

##  Nope, the small resonating cap is wired  directly in parallel with the choke.  That forms a 
parallel tuned circuit, killing the 120 hz component. Any cap after that, that is wired from B+  to
B- just kills any residual 120 hz components, plus harmonics of 120 hz.  HV filter caps are not wired
from B+ to chassis, they are wired directly between the B+ and B-.   Any HV meter is also wired 
directly between B+ and  B-.  Old ARRL handbooks will depict HV meters wired between  B+  and chassis,
which is incorrect..and more fubar. 

##  John lyles designed a HV supply for a FM broadcast TX.  For the resonating cap, he used the 
.9 uf at 5 kv rated small oil cap  you will typ see in any microwave oven.    He used 2 of em in series,
so  .45 uf at 10 kv.   Both caps sent to the choke maker..who builds the resonant choke around the
.45 uf combo.   On any single phase setup, the component you are trying to get rid of is always 2F,
or in north america, 2 x 60 hz  = 120 hz.    In japan, UK, etc, its  2 x 50 hz  = 100 hz.   For 3 phase
setups, it now becomes 6 F, or  300 hz in the UK and  360 hz  in north america. 

##  resonate the choke at 120 hz, and the caps will explode every time, it has to resonate just above
120 hz.   Ask anybody who has tried it. 

##  the typ NON resonant choke setups back in the day consisted of a pair of tube rectifiers, then
into the swinging choke, then into the fixed choke, followed by a pair of paralleled small value oil caps..then the huge bleeder assy. 

##  back in the day, typ HV oil caps were like  2 uf, 4 uf, and  6 uf for a big oil cap.   Plate xfmrs back then were high Z types,
not made for the high peak currents of a high C filter setup.  Typ high Z plate xfmrs had a lot of  DC resistance  across the sec windings. 
They also used a CT, since the tube rectifier setup consisted of a FWCT  config.   The B+ came off of the CT of the fil xfmr. 

##  It isnt 1957 anymore.  Tube rectifiers, high Z, centered tapped plate xfmrs, tube fil xfmrs with the HV CT, real small value oil caps,
fixed chokes, swinging chokes, and resonant chokes have gone the way of the do-do bird.   The big hypersil + loads of filter C is the
ticket. Buddy with the 2 x GS35B on 6m... the B+ only drops 50 vdc under a full load of   4.1 kv  and 2A.    Then another 100 vdc drop cuz
of the 50 ohm glitch assy, which is a necessary evil. 

##  Even the plate xfmr used in my drake amps only has 9-10 ohms across its  940 vac sec. 
Its a FWDoubler.  2650 on RX... 2600 on idle, keyed, with no drive, and 2520 vdc  with a 800 ma load. 
Its aprx a 850 va CCS xfmr, nothing special.     120 lb pole pigs with a 4800 sec typ have a 19 ohm sec.
My even bigger dahl is just 6 ohms across its  5200 highest tap, and only   2.65 ohms across it lowest tap
at 2300 vac.  My 46 lb dahl is 24 ohms across its  2700 vac highest tap. 

##  I have caseloads of  2100 uf at 450 vdc lytics, and also 2300 uf, and also 10,000 uf.   These surplus
large value lytics are the ticket when used in conjunction with a low Z plate xfmr.  HV meter barely flickers on 
ssb.   IMO, henry radio wasted a lot of effort pursuing their FWB + resonant  choke   HV supplies.   They ended up
with heavy console units that typ weighed in at 185 lbs.   The henry 8K  combo RF deck + pwr supply weigh in at
350 lbs, yet the supply is only good for 2 kw CCS rf output.   Heavy yes, heavy duty, no. 

Jim  VE7RF