Re: MOT Caps DC Limit

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Conner <steve@xxxxxxxxxxxx>

> I will run it at a
> higher BPS than this, but
> knowing that the capacitor will not get fully
> charged.

Are you thinking that it doesn't charge fully if
there's not enough time to complete a half cycle of
the charging circuit resonance between breaks? This
isn't the case, the capacitor always charges to twice
the DC bus voltage. The inductor current just becomes
continuous (it never falls to zero)

Craggs and Meek argued that continuous current is
actually more efficient in their papers on spark-gap
radar modulators, and Richie Burnett covers the theory
on his site.

Of course this doesn't take into account IR drop in
the charging chokes and sagging of the DC bus voltage
under load, both will be greater at higher bps.

I ran my DC coil with three times the original design
tank capacitance at the weekend, without bothering to
change the charging choke. The current must have been
well continuous but it didn't seem to reduce the power
output that much- I was blowing 5A variac fuses and
partly melted the gap electrodes. From the melted
remains, it seems I got brass-plated steel screws
instead of solid brass, yuk!

Steve Conner