Re: DC Resonance Charging Advice Sought

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

Original poster: "Bert Hickman by way of Terry Fritz <teslalist-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Hi Dave,

Nice looking system! My responses are interspersed below...

Tesla list wrote:
>Original poster: "Dave Kyle by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><dave-at-kyleusa-dot-com>
<SNIP>
>I have now completed and tested to 8KVDC (without load) the DC power supply
>which can be seen here:
>http://home.austin.rr-dot-com/dkyle/images/temp/dc_tesla_ps.jpg. For scale the
>base disk is two feet across. You will note the very large black power
>transformer, full wave rectifier and de-Qing circuit, smoothing capacitors
>with safety bleeders and grey charging inductor.
>Specifications are as follows:
>4.700KVAC 775VA transformer (6.65KVDC rectified)
>7uf -at- 10KVDC of smoothing capacitors
>20Henry -at- 15KVDC inductor
>Under construction:
>.02uf -at- 20KVDC cap
>0 to 500bps RSG
>4 inch x 25 inch secondary with 1400 turns of #26 gauge wire
>6x24 inch toroid
>15 turn primary (tuned at 11 turns)
>Advice needed on the following:
>1.) I have yet to resolve the system grounding. Is it advisable to ground
>the center point of the main transformer for safety (like an NST)? Or would
>it be better to simply ground the negative side of the DC power supply? Or
>let it all float and just ground the secondary?

Grounding the center tap of the HV transformer's secondary will result in 
the minimum stress to its insulation system. The next best would be to 
ground the negative side of the supply. The secondary side should not be 
allowed to float, since you want to insure a solid path to ground for any 
streamer hits to the primary circuit.

>2.) I am assuming this transformer is not shunted (current limited) but
>short of dismantling it how can I tell? DC resonance charging is self
>current limiting so that will not be an issue but I would like pull current
>slightly higher than the transformer's rating.

The HV transformer looks like a standard plate transformer and it has no 
shunts.

>3.) Assuming the transformer is not shunted would there be any benefit to
>adding PFC caps?

Probably not - the load that the HV transformer will see will primarily be 
capacitive, so PFC's on the primary will not appreciably reduce current. 
There's no reason to capacitive ballasting, since (barring reactor 
saturation) current limiting is accomplished by the charging reactor.

>4.) I have noticed in some of the very few DC coils documented on the net
>that a clamp diode and air inductor are sometimes added to the charging
>circuit presumably to protect the supply and caps from over voltage and
>transients. Can anyone comment on the need for this?

The additional protection circuits are primarily there to protect the 
de-Qing rectifier and charging reactor from high amplitude voltage 
reversals when the spark gap fires (due to Blumlein effect when longer 
length transmission lines or coax are used to connect the HV supply to the 
spark gap and tank circuit). If you minimize the distance between the 
output of the power supply and the rotary spark gap you should be OK.

>Dave
>=========================================
>Dave Kyle
>Austin, TX USA
>Email: dave-at-kyleusa-dot-com
>
>.

Good luck and best regards,

-- Bert --
-- 
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