[Amps] Alpha vs. Henry

[Gary Schafer]

The choke needs to be resonant at 120 Hz with only bleeder current, not
higher in frequency. Yes there are very high voltages across the choke at
resonance. You need a very good cap and voltage capable choke.

When you draw more current from the supply the choke inductance drops and
the resonance point shifts higher in frequency. 
If the choke was not resonant with low current there would be no need for
it.

Peak power line and transformer current will be much lower with the choke
than without.

73
Gary  K4FMX

> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]
> On Behalf Of Jim Thomson
> Sent: Monday, April 04, 2011 6:18 AM
> To: amps at contesting.com
> Subject: [Amps] Alpha vs. Henry
> Importance: High
> 
> Date: Sun, 3 Apr 2011 21:00:39 -0400
> From: "Gary Schafer" <garyschafer at 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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