Re: Primary dummy-loading

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Original poster: "R.E.Burnett by way of Terry Fritz <twftesla-at-uswest-dot-net>" <R.E.Burnett-at-newcastle.ac.uk>


Hi Gary, all,

> I was wondering if anyone has come up with a way to dissipate the bulk
> of each primary bang in something less hazardous to my basement (and me
> and my scope) than streamers.  I was thinking of either some kind of
> dummy load resistor in series with the primary ?

The answer is YES !  Connecting a resistance in series with the primary,
(or instead of the primary)  works great to stop the sparks from the
toroid while making adjustments to the gap.  It de'Q's the primary ;-)

I posted a message about using linear halogen lamps to achieve this in
1999, which I include again for reference:

							-Richie Burnett,
* Hi all,
* 
* For about the last month I have been dinking around with various
* sync and async rotaries,  paying particular attention to
* charging efficiency.  Some will remember a post several months
* ago asking about modifying a TC to produce no sparks so that
* measurements and fine adjustments could be made to the charging
* system without the noise and danger of a 3 foot arc buzzing
* around the toroid !
* 
* It was generally agreed that removing the secondary is BAD. The
* problem is finding somewhere for the tank capacitor's energy to
* go.
* 
* What I have done over the last few weeks,  is replace my primary
* winding with a chain of 3 halogen filament lamps.  The 1000W kind
* used for outdoor security flood-lights. I was originally hesitant
* to do this,  because I feared that the filaments may "fuse" under
* the high peak discharge currents.  However this idea seems to
* work well and provides many advantages to anyone wanting to study
* the charging behaviour or make fine adjustments to rotaries:-
* 
* 
* 1. There are no toroid sparks,  hence less danger and less noise.
*    (Also a far safer environment for using an oscilloscope.)
* 
* 2. Peak currents are lower.  The current when the spark gap fires
*    is limited due to the resistance of the halogen lamps.
*    This reduces wear and also dramatically reduced spark gap
*    noise to a quiet buzz. (Even the safety gap made a quiet pop.)
* 
* 3. Less RF interference.  Since the capacitor now discharges into
*    a resistive load,  the energy is dissipated in an exponential
*    type decay rather than the usual damped ringing.  Therefore
*    there is little RF generated and I found that television
*    interference was almost eliminated completely.
* 
* 4. Lamp brightness provides an indication of power throughput.
*    Adjusting rotary phase for maximum brightness may be a good
*    alternative for those without a scope and HV leads.
* 
* 5. Charging behaviour is the same as with a normal TC.  The
*    substitution of the halogen lamps for the primary has little
*    effect on the low frequency charging behaviour of the system.
* 
* I just thought I would share this,  as it has enabled me to
* carry out many hours of work on sync rotary charging without
* keeping the neighbours awake and messing with there TV's.
* I guess it would work just as well for static gap and async TCs.
* 
* If anyone plans to try this please rate the series chain of lamps
* generously for the power you expect to process.  I used three
* 1000W 240v lamps in series,  and they lit dimly while running at
* 600 Watt.  Also bare in mind what would happen if a lamp went
* open circuit !  (Dangerous charge left on capacitor !!! )
* 
* 					- Richie
* 
* 					- In sunny Newcastle.