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Re: [TCML] discharging caps through NST



Thanks for replies.

I bought 4, 35kv doorknob caps , used in parallel to avoid multi caps which

may well work out similar price.  (my 4, 2700pf doorknobs were £66, rated at 35kv).

I will take Steve's advice and put a bleeder across  them. Using car jumper cable to connect

them to primary and spark gap because I read that RF current can be very high.


On 04/02/2018 17:40, undisclosed recipient via Tesla wrote:
I made mine with 2200 volt caps…  I have yet to find caps that can handle 15kV outside of public utility units.

On Feb 4, 2018, at 8:56 AM, Steve White <steve.white1@xxxxxxxxx> wrote:

If you were using a single capacitor or multiple capacitors in parallel only, then in theory you shouldn't need the bleeder resistors because, as you say, the capacitors will naturally discharge into the transformer secondary with no harm to the transformer. However, if you are using multiple capacitors in a series-parallel configuration, then there is no guarantee that all of the capacitors will discharge into the transformer secondary. For that configuration, bleeder resistors are highly recommended.

There is a second reason for using resistors when capacitors are wired in series. The resistors spread the charging voltage evenly across the series capacitors. This prevents some capacitors from being exposed to excessive voltage due to different internal resistance. This is why parallel capacitors are preferred over series capacitors when feasible. When a series-parallel capacitor configuration is needed then bleeder resistors should always be used.

There is also the small chance that your transformer secondary could have failed in which case the capacitors will not have discharged.

Given all of this I would always install bleeder resistors.

----- Original Message -----
From: "Albert" <Animation@xxxxxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Sent: Sunday, February 4, 2018 7:28:32 AM
Subject: [TCML] discharging caps through NST


Hello all, my first posting ....

I am building a standard tesla coil (NST, 15kv at 30 m/a etc)

When working, if I switch off when the caps are charged but the spark
gap hasn't yet fired,

(say they are charged to 10kv), than the caps can now discharge back
through my NST secondary

via the tesla coil primary coil as all are in series.

My NST secondary resistance measures 20k ohms.  So 10kv is put

across this equating to 1/2 AMP !!.  Can the NST fine secondary windings
take this continually?


Also as the caps discharge quickly via the NST anyway,do I need bleed
resistors across the caps?

(4 doorknobs in parallel)


Thanks.


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