Date: Wed, 13 Dec 2017 21:16:22 -0500
From: Ron Youvan <ka4inm@gmail.com>
To: amps <amps@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
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