Re: [TCML] charging chokes??

[G Hunter <dogbrain_39560@xxxxxxxxx>]

A DC charging choke is just an iron-core inductor
placed in series with the load.  Inductors are energy
storage devices.  When the tank cap is charging from
the HV supply, current flows through the charging
choke, storing up energy in the form of a magnetic
field.

When the tank cap reaches peak charge, choke current
stops.  Without steady current, the magnetic field
cannot be sustained, so it collapses back into the
windings of the choke.

The relative motion of the collapsing magnetic field
induces more current in the choke windings.  This
extra surge of current charges the tank capacitor
beyond its initial peak charge, up to as much as 2X
the original charge (although usually a bit less in
real circuits).

My explanation is rather simplistic.  For a better
description of how this works, see

http://www.richieburnett.co.uk/dcreschg.html#resonant

BTW:  There's nothing new about DC resonant charging
choke power supplies.  Some WWII-era magnetron radar
sets used the DC charging choke trick to increase the
bang voltage in the pulse forming network.

How is it constructed?  I've seen two main types.  

The most common kind of DC charging choke (sometimes
called a "reactor") looks exactly like a regular
closed-shell AC power transformer, except that it only
has two connections to a single winding.

The other kind I've seen has a straight, stick-type
core covered by a simple solenoid winding.  The core
is usually square in section, made of a stack of
rectangular transformer laminations.

Whether shell-type or straight-cored, high-powered DC
charging chokes can be quite bulky and heavy--just
like our power transformers!

Search for "inductor", "DC choke", and "DC reactor" on
e-bay and you will get a few hits.  The closeup photos
of the various chokes and their data plates are far
more useful than all my blather.

Greg


--- Ben Sneath <bsneath@xxxxxxxxxxxxxxxx> wrote:

> exactly how does a choke boost a dc voltage?
> am i missing something about the choke's
> construction, how
> is it wound?
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