Hi Steve,
To be perfectly honest, since I have no formal training in electrical engineering, I’m afraid your inquiry is beyond my collective expertise. 🤪 I will say that I’ve heard that the voltage reversal vs shot life issues can be reasonably dealt with by choosing a cap whose maximum voltage rating is a minimum of 3x the peak input AC voltage (rms x 1.41), assuming that it is properly designed with a low loss dielectric system. My transformer can produce up to 16.8 kvAC so 16800 x 1.41=23688, and 23688 x 3 = 71,064. My primary tank capacitor is rated at 75 kV, so I should be ‘good’.
David
Sent from my iPhone
> On Sep 13, 2020, at 12:38 PM, Steve White <steve.white1@xxxxxxxxx> wrote:
>
> Hi David,
>
> I've always wondered if a ARSG has some negative effect on capacitor life. With a ARSG essentially firing at slow-rolling random times it seems as if many of those firing events would be during capacitor voltage reversals during the charging process. Of course the frequency of the 60 Hz charging voltage reversals is much lower than the voltage reversals experienced in the primary coil tank circuit. Since percent voltage reversal is a key capacitor lifetime parameter, it seems like something to consider.
>
> That potential problem can't happen with a SRSG because the firing points are nominally at 0 and 180 degrees for a 120 PPS system or at 0, 90, 180, and 225 degrees for a 240 PPS system.
>
> Maybe the effect is negligible.
>
> Thoughts?
>
> Steve White
> Cedar Rapids, Iowa
>
> ----- Original Message -----
> From: "David Rieben" <drieben@xxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Sunday, September 13, 2020 11:31:24 AM
> Subject: Re: [TCML] Asynchronous versus synchronous gaps, was Old Post
>
> Hi Jan,
>
> Yes, thank you for highlight a very important aspect of async SG operation that I failed to mention in my posting. Higher bps rates that are several times the mains frequency, in addition to to generous power, are essential for optimal asynchronous coil operation. ~350 bps seems to be the approximate “sweet spot” for my pole pig powered and async spark gap driven coil. I use a DC permanent magnet motor (from a treadmill, I believe) for my rotary gap drive motor, with a rectified and variac controlled input to affect basically infinite speed control of 0 - 3500 rpm. Since there are 8 flying electrodes on my rotary disc, and the motor is rated for 130 VDC and 3500 rpm, I typically set my speed control variac between 70 and 75 on the dial for the “sweet spot”, with the variac set to deliver 0-120 volts (not 0-140 volts) output.
>
> David
>
> Sent from my iPhone
>
>> On Sep 13, 2020, at 9:58 AM, jan@xxxxxxxx wrote:
>>
>> -----Original Message-----
>>
>> From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of David Rieben
>>
>> Sent: September 11, 2020 7:01 AM
>>
>> To: Tesla Coil Mailing List
>>
>> Subject: Re: [TCML] Old post
>>
>>
>>
>> Hi Shaun, Steve,
>>
>>
>>
>> Although synchronous firing (w/LTR tank capacitor) can be quite advantageous
>> for the rather limited available? power with a typical NST driven spark gap
>> coil system, from personal experience, I have found the output can be just
>> as impressive with asynchronous spark gap operation and higher bps ranges w/
>> a smaller than resonant tank capacitor with the more copious available power
>> with PT or pole pig driven spark gap coil systems. And it?s a whole lot
>> easier! ?
>>
>>
>>
>> Just my $.02,
>>
>> David
>>
>>
>>
>>
>>
>> Hi,
>>
>> as has been pointed out, asynchronous gaps are very effective att higher
>> BPS, but at low BPS synchronous are better. At higher BPS some bangs will be
>> a bit off in timing, but others will be at the right point. The energy left
>> in the ballast after less successful bangs will be used in the next bang, so
>> it all evens out over time. But at one bang per half period, the timing is
>> very critical and a synchronous gap with phase control is a must.
>>
>>
>>
>> I have done some measurements and discuss these issues at my web site
>> https://www.sthlmteslacoil.se/measurements.html
>>
>>
>>
>> So successful coils could be designed with either type of gap, depending on
>> the BPS. But more important is the resonant charging concept. A good
>> resonant design could supply three or four times the energy compared to an
>> arbitrary design. I discuss these issues also at my web site.
>>
>>
>>
>> Regards,
>>
>> Jan
>>
>> Stockholm, Sweden
>>
>> _______________________________________________
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>
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