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Re: DC power



Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<youngs-at-konnections-dot-net>
> 
> Chris,
> 
> Good for you - DC is fun to experiment with!  One suggestion.  Do NOT charge
> your tank cap directly from your DC supply.  This is very hard on the tank
> cap and the DC filter caps.  Roughly half the charging energy gets
> dissipated in the resistance of the circuit, i.e. the wiring and the caps
> themselves.  Adding resistors between the filter and tank cap reduces
> stress, but again, you end up wasting half the energy in that resistor.
> 
> Instead, charge your tank cap through your primary, then discharge it to
> ground through your primary.  This is much more efficient.  Might as well
> put the charging energy into your coil instead of heating and stressing
> components.
> 
> As far as resonant charging, you only need 20 Henry or so to do the job, as
> long as you keep the BPS above about 300 BPS.  Below that, it will power-arc
> when the reactor saturates.  A couple of MOT secondaries in series will
> work.
> --Steve

	Haven't really been following this, but wanted to point out that the
standard DC resonant charging circuit for radar pulsers uses an HV
blocking diode in series with the (tank capacitor side) of the
inductor.  It the sparking rate is below a critical value, the tank
capacitor is charged to twice the supply voltage (at least after the
first discharge) and just "sits there" waiting for the next switch/RG
closure.  Very high power modulators using rotary gaps were widely used
during WW2, as they were relatively cheap and relible and had quite
adequate timing stability for non-coherent pulse radar work.  Triggered
spark gaps of various kinds, operating both in air and with
high-pressure gas fill in a sealed tube, were also quite common.  

Ed