[TCML] 20KV primary drive voltage tips ?

["Chris Swinson" <list@xxxxxxxxxxxxxxxxxxxxxxxxx>]

Hi all,

I am working on a 20KV res-charging design to boost 10KV to 20KVDC. I forget 
the size of the inductor but the break rate will be 100 or 200bps. I plan to 
use a sync motor to keep the timing spot on. So the RSG will have a suitable 
number of electrodes on the disc.

So my first question really is has anyone built a low power 20KV system. 
This will only be 500watt prototype ( don't have room or a NST for anything 
bigger anyway).

I know my 10KV primary is spaced out about 0.5" so I assume a 1" gap between 
turns will be needed ?

The 20KV drive should help spark gap quench times ?

Ideally I want to aim for 1st notch quench and keep the transfer cycle time 
to 3 cycles maximum( so >0.3K needed)

20KV will probably suffer from corona on the primary, but that will have to 
be delt with if/when it happens.

I also want to keep the coupling as tight as possible. Going by my 
simulations 0.38K seems to be the maximum before hitting problems. Also 
should a cone or vertical primary be used ?

Onto the key points now, the last system I built was 500khz 10KV, so 20KV 
should allow a 1mhz coil to be used.  Really its half the inductance and 
double the voltage input to get the same spark output. A bit of a long story 
for another day that one!

The secondary will be using at least 0.8mm dia cable ( its what I used on my 
500khz coil ) I want to half the inductance ( half the turns probably) which 
will also half the resistance, though now I can afford to use double the dia 
of wire to keep the secondary the same height as my 500khz coil was.

I am aiming for 1ohm DCR on the secondary. the larger dia wire should help 
with the running at 1mhz.

The secondary form will be 6.3" dia and about 50-60" tall. A lot of figures 
to crunch up and some compromises no doubt.

The design is to start at 500watts input power as before, keeping the 
secondary size physically the same size, but just using a larger dia wire. 
Will run at a higher frequency and have less turns/inductance hence the need 
for a 20KV input.

Well that's the overall design idea I am aiming to build. I have my RSG disc 
and sync motor built, also have the charging choke, collected a fair few MMC 
caps to get the values I will probably need. So all pretty much ready to 
start work on the primary/secondary design now.


There are probably other factors I've not taken into account yet too.. so 
plugging for ideas and help before I spend hours building something which 
could melt at first light :-)

Cheers,
Chris


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