Re: DC Reso Charging

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <teslalist-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

On 25 May 2003, at 15:50, Tesla list wrote:

 > Original poster: "Jolyon Vater Cox by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
 >
 > Dear List,
 > Would it be possible to implement DC Resonant Charging for a TC with a dual
 > ignition-coil power supply, by using the secondaries of a couple of the
 > more modern flyback transformers (the cylindrical models with integral
 > rectification) as charging chokes? Using flybacks in this way, would it not
 > be possible to integrate all the rectifiers, charging chokes plus de-Q-ing
 > diodes into two small units?
 >
 > BTW, I did once try to measure resistance of the HT winding of a flyback
 > -it is so high that practically impossible to read on a normal multimeter,
 > so the current flowing through it in normal operation must be very low -a
 > milliamp or two at most.

What value constitutes "so high"? The resistance of the windings is a
few hunndred Ohms. The difficulty you are probably experiencing is
because you don't get direct access to the windings thanks to
trippler capacitors and diodes built-in. The diodes alone have a
substantial forward drop and one of the caps at least stops you from
"seeing" the bottom end of the winding at a pin coming out of the
potting.

 > I would imagine the inductance of the secondary winding of a flyback
 > transformer must be fairly high although the Q might not be
 > -due to high resistance of the winding might although this might not be a
 > bad thing considering the de-Q-ing diode normally included in DC reso
 > setups/ what do you think?.

They are actually used in resonant modes for rapid beam flyback
(where the name comes from), thanks to airgap energy storage.

Malcolm

 > Is it at all likely the current from the ignition coil will damage the
 > flyback winding when it is used in this way, and would the total PIV of all
 > the diodes in diode-split winding be likely to be sufficient to withstand
 > the reverse voltage?
 >
 > If it is possible for a flyback secondary to provide the services of a high
 > inductance coil capable of withstanding high voltages
 > with the bonus of the diodes to provide rectification and de-Q-ing, are
 > there likely to be any other problems which could prevent these coils being
 > successfully used as charging chokes in  small DC-reso charging schemes,
 > for example, in mini TCs?
 >
 >
 >