Date: Sun, 3 Apr 2011 21:00:39 -0400
From: "Gary Schafer" <garyschafer@comcast.net>
Subject: Re: [Amps] Alpha vs. Henry
Not according to Collins. They say that the choke should be resonant at 120
Hz with minimum critical current, eg bleeder current, which keeps voltage
from soaring.
As current draw increases the inductance of the choke will drop, going out
of resonance and increasing ripple voltage out of the supply.
73
Gary K4FMX
&& resonant chokes schemes are steam engine technology..and buy you
absolutely ..nothing !
Resonate the choke at 120 hz... and the peak V across both the choke and the
resonating cap will be
through the stratosphere. Both will blow up, the choke will be ruined, and
the cap will explode.
&& To build em correctly, you have to suck one helluva lot of bleeder current.
At that point, the choke should
be resonant ABOVE 120 hz. OK... now when you suck loads of plate current, the
choke L will drop a bit...and
resonance will INCREASE. IF the coke resonates BELOW 120 hz...with just
bleeder current... you are in trbl.
When sucking plate current, the resonance will increase, and when it passes
through 120 hz....Kaboom every time.
&& It`s a stupid flawed design anyway, imo. The 8 k ultra runs 5400vdc NO
load. To pull this off, they use a
6000 vac plate xfmr. .9 x 6000 = 5400 vdc no load...except for the 5 x 20k
at 100 watt ccs wirewounds..all in
series. That`s 300 W CCS of bleeder..which is a blast furnace ! Each 100w
resistor is dissipating 60 w...and they
run extremely hot. OK, now if just any ONE of those bleeders ever open`s
up... watch out. The B+ will soar to
1.414 x 6000 = 8500 vdc. At that point those failure prone oil caps used in
the henry amps will become IED`s.
The tube may well be next, along with bypass caps, and everything else you can
think of.
&& The regulation on the 8k is nothing to brag about either. 4800 vdc with
just 1.25 A of plate current. That`s a 12 %
drop.. It drops 800+ vdc So much for the good regulation. Both the plate
xfmr and the mating choke are best seller`s when
dahl was still in business.
&& Here henry used a 6000 vac xfmr....when a 3800 vac xfmr + FWB would have
worked a helluva lot better.
Even a 1900 vac xfmr and a FWD would have worked better. A 6000 vac xfmr
is a poor utilization of it`s
winding. Then toss in the huge,heavy choke + heavy oil caps. The classic
resonant choke setup only filters 120 hz to boot. It won`t
reduce the ripple at 240,360,480 hz. So they still need a mess of oil caps.
&&& A simple 3800 vac hypersil xfmr, or similar... + a BIG C filter will run
rings around the resonant choke scheme. Why
spend $$$ on plate xfmrs with massive oversized sec V ratings = smaller ga
wire used= low current capability....then toss in the
meagbuck heavy choke = 1921 technology.
later... Jim VE7RF
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