Hi Teddy,
For my pole transformer (10 KVA rating) powered system I made the decision to limit the input power to 4.8 KVA wall power. This is done through the use of an adjustable air gap ballast that I made which is very similar to the one that can be seen on Richie Burnett's web site. I can very easily increase that power up to about 10 KVA by increasing the air gap spacing. I picked the 4.8 KVA power level because it can almost fully charge my capacitors: 45 nF charged to 88% at 240 BPS according to JAVATC.
As you may know, pole transformers are not current-limited, so a means must be provided to limit the current, hence the ballast. The other reason that I chose this power level is not to push things too hard. When I built my SRSG (this was my first RSG) I only used 0.125 inch tungsten on the flying electrodes. Although this seems small, they seem perfectly happy with the cooling they get at 3600 RPM and I see no noticeable erosion. The stationary electrodes, which are 0.1563 inches, actually erode more because the cooling isn't as good and they are fired 4 times as often. If I were to build this SRSG again I would use larger diameter tungsten electrodes. So I am not certain how well the SRSG would work with these electrode sizes above power levels of 5 KVA. The limiting factor in my power cabinet is the variac. It is a large 240 volt General Radio unit rated at 25 amps but can be pushed higher for short periods. So my ultimate power limit with this variac is probably around 7.2 KVA, assuming 30 amps through the variac. I am perfectly satisfied, for now, with my 8-foot sparks.
In answer to your question, the capacitance can be made bigger if I allow more power. I have enough extra Maxwell capacitors to go to 60 nF if I want. But this would require a power level beyond my current setting of 4.8 KVA to take full advantage of that extra capacitance. For the reasons mentioned earlier, I don't want to do that right now but I might in the future if I start to get "spark envy".
Believe it or not this was my first tesla coil. I believe in starting big if you know what you are doing.
Steve
----- Original Message -----
From: "Tedd Dillard" <tedd.dillard@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Wednesday, March 28, 2018 6:40:24 PM
Subject: Re: [TCML] Unexpected RSG phase shifter behavior
Gentlemen,
I am a newbie just starting my first coil and everything I know comes from
the last several months of reading. The TCML is especially helpful.
Reading Richie's paper on SRSGs and resonate charging it seems that the
main point is to fully charge the caps.
If the simulation says you are getting 88% and that is not changing with
phase shift doesn't that suggest the caps are not big enough?
Teddy
On Mar 28, 2018 6:27 PM, "phil" <pip@xxxxxxxxxxx> wrote:
>
> Steve
> As your running the 60Hz equivalent of my own coil setup in the UK (200bps
> @ 50Hz), you should, when correctly in phase, have four firing peaks of
> equal voltage. This gives a very distinct, characteristic sound or 'drone'
> to the coil, and is what I use to find and set the correct position. (only
> works on 200bps , and to a lesser extent on 400bps, 100bps always having a
> 'rasp' sound to it regardless, and 300bps always sounding 'ragged')
> Listen to when my coil (deliberately started out of phase) is put onto
> phase at 55 seconds in (link starts at 45 seconds):
> https://youtu.be/yRBqDZCP0jc?t=45 Also the same later on where I put it
> out of phase to make it hit the floor more: https://youtu.be/yRBqDZCP0jc?t
> =234 (it happens at 4:05)
> You should be hearing a difference on yours though, if all is correct. You
> will get some voltage reversal though, as the firing point when all the
> caps voltage peaks are equal is after the sine wave peak.
> As John says if you tune it enough off phase you can get a 'pseudo' 100bps
> setup, but having two high peaks and two low ones per 60 Hz cycle. This may
> over volt the caps though, so I wouldn't recommend it.
> I would check with a strobe that you are getting the full 90 degrees shift
> you need, if not you could find the area you want is just out of reach.
> Bear in mind though (or you may have already found out) that getting the
> full 90 degree shift is achievable only at the cost of having a higher than
> comfortable voltage (from the motor's point of view) being fed to it.
> On a 240v UK set up I've measured as much as 270+ volts being fed to the
> motor with the wrong cap values in place, so that's a good way to kill a
> motor if you're not careful.
>
> (Once you do find the sweet spot it's best to move the disc on the motor's
> shaft so that the best position is midway in the sweep of the phase
> controller.)
>
>
> Phil Tuck
>
>
> On 27/03/18 04:52, Steve White wrote:
>
>> I have had my big SGTC running for about 9 months now. Here are the
>> salient specs:
>>
>> * 8.6" x 39" secondary
>> * 9" x 30" top load
>> * 45 nF of primary circuit capacitance
>> * RSG with 4 rotating electrodes and 2 stationary electrodes, 3600 RPM,
>> 240 breaks per second (4 per 60 Hz cycle at 0, 90, 180, and 270 degrees)
>> * Pole pig as power source
>> * 4800 watt wall power
>> * Maximum spark length is about 8 feet
>>
>> I also built an electrical phase shifter, as others have, based on a
>> variac and capacitors. I confirmed with my oscilloscope and an optical
>> sensor that I can get about 0 to 90 degrees of phase shift by turning the
>> variac knob. Before I added the phase shifter, I used an optical sensor and
>> oscilloscope to accurately set the firing points at 0, 90, 180, and 270
>> degrees of each 60 Hz cycle.
>>
>> My question concerns the apparent non-effect of the phase shifter on
>> spark length. With the coil running, as I adjust the phase shift, I see no
>> apparent change in the spark length. Does anyone have any thoughts as to
>> why this would be? I am perfectly satisfied with the coil's performance, I
>> just can't explain the apparent non-effect of the phase shifter.
>>
>> Steve
>> _______________________________________________
>> Tesla mailing list
>> Tesla@xxxxxxxxxxxxxxxxxx
>> https://www.pupman.com/mailman/listinfo/tesla
>>
>
> --
> Regards Phil www.hvtesla.com
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxxxxxx
> https://www.pupman.com/mailman/listinfo/tesla
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxxxxxx
https://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxxxxxx
https://www.pupman.com/mailman/listinfo/tesla