[Amps] Power factor and choke vs resonant-choke input supplies

Harold Mandel hmandel at barantelecom.com
Thu May 10 16:18:35 EDT 2007

Dear Barrie,

Now you have a project!

First thing: See if your choke winding has a  gap. That's the big ticket
hurdle, because without a gap, it can't swing.

Next, use your B&K LCR meter to measure the inductance. Can do, yes?

Oh, well, no problem.

Build a rectifier out of some diodes and put some juice into the choke,
but make a 
C-input filter with some small amount (2~4 uF) of capacitance and hook
up a load resistor
that will be more than the idle current you expect to crank.

Hook up an ammeter in the choke line. Turn the power off and put a
capacitor across the
choke leads. Lookit the amperage, write it down.

Start adding or substituting caps with lesser capacitance across that
choke puppy and
see where your jump in current occurs. 

You could just hook up and do it without any juice at all, but that
won't give you
the dynamic performance point, which is always different than the
XsubC = XsubL point.

Anyway, send Tom Rauch an e-mail and ask him about testing chokes. (Har
de Har, Har, Alice!)

Be careful out there. The streets are a jungle. 


-----Original Message-----
From: Barrie Smith [mailto:barrie at centric.net] 
Sent: Thursday, May 10, 2007 3:46 PM
To: g3rzp at g3rzp.wanadoo.co.uk; Borislav Trifonov; Harold Mandel
Cc: amps at contesting.com
Subject: Re: [Amps] Power factor and choke vs resonant-choke input


Resonant-chokes may be placed in the negative lead?

Also, could you elaborate on the "close to it" resonance?

I have a largish power supply, using a Peter Dahl
resonant-choke/capacitor combination,  that has never worked properly.
I'd like to improve or rebuild the power supply so that it did work

73, Barrie, W7ALW

----- Original Message -----
From: "Peter Chadwick" <g3rzp at g3rzp.wanadoo.co.uk>
To: "Borislav Trifonov" <bdt at shaw.ca>; "Harold Mandel"
<hmandel at barantelecom.com>
Cc: <amps at contesting.com>
Sent: Thursday, May 10, 2007 10:34 AM
Subject: Re: [Amps] Power factor and choke vs resonant-choke input

> Why are you particularly worried abuot the power factor?
> Some simulations a colleague did some years back suggests that in
the choke shouldn't be resonant, but very close to it, such that the
looks like a very much bigger inductance rather than a straight
at the ripple frequency. This is done for minimum load, as the choke
inductance will decrease somewhat as the load increases. That's how I
succesfully use tuned choke input: in addition, I filter in the negative
lead, so you don't need to worry about the case to innards insulation n
capacitor when it's reasonable size metal cased oil cap. Incidentally,
chokes were always obtained by a process f scrounging - I've never
one yet! That includes a massive 10H 1 Amp one set aside for a
> I believe Tom, W8JI, has some hair raising tales about his first
at resonant choke input supplies....
> 73
> Peter G3RZP
> _______________________________________________
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> Amps at contesting.com
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