Steve you said in your initial post that your SRSG motor was 3600 rpm. In
your last post you said the motor armature had four flats machined into it.
I understand that a 3600 rpm motor has only two poles so I would expect the
rotor to have only two flats.
What am I missing.
Teddy
On Mar 29, 2018 1:02 PM, "Steve White" <steve.white1@xxxxxxxxx> wrote:
> Hi Teddy,
>
> Keeping 4 variacs in balance must be a challenge. Did you use a
> current-balancing transformer for each pair? They are used to balance the
> current between transformer pairs to prevent one from overloading the
> other. If you don't know what that is, look in the Superior Electric
> catalog. You can make one yourself with a large toroidal core. I originally
> planned on using two of the General Radio W50 variacs (240 volt, 25 amp) on
> a common shaft with a current-balancing transformer. I went so far as to
> make the transformer but I never used it. I decided that a single GR W50
> variac would supply all of my power control needs without the complication,
> size, and weight of 2 large variacs.
>
> I measured the phase shift with the motor running with the load of the
> rotating disk and electrodes. I used an optical sensor and oscilloscope to
> measure the phase shift. The phase shift is real. I don't remember what my
> maximum phase shift was but it was close to 90 degrees. My phase shifter
> uses a large (20 amps at 120 volts) Superior Electric variac. I can't
> remember how much capacitance I used. I want to say that it is about 200
> uF. I know that I used 4 motor "run" capacitors which I think were about 50
> uF each. I kept adding and removing capacitors until I got the maximum RMS
> voltage into the motor below 130 volts. My motor is a modified 1/2 HP
> induction motor with 4 flat spots machined into the armature. One thing
> that I do remember is that when I looked at the power coming out of the
> phase shifter at the motor input, the waveform was far from sinusoidal with
> a lot of distortion. This doesn't seem to affect the motor. I even see the
> distortion without the phase shifter.
> So that is a mystery.
>
> When you make your SRSG the most important thing is to get that rotating
> mass VERY accurately balanced especially if you are running at 3600 RPM.
> The electrode mounting holes must be VERY accurately located and drilled.
> Any mounting hardware for the flying electrodes must have identical weight
> for each electrode. The rotor must be perfectly round or as close as you
> can get it. If not, the whole thing will shake itself to pieces. I now have
> a lathe and milling machine which I did not have when I made the SRSG.
> These would have made the job a lot easier but I came up with some creative
> ways to do this without those machines. I found that building the SRSG was
> the most difficult part of building the tesla coil because it requires a
> lot of mechanical precision.
>
> Steve
>
> ----- Original Message -----
> From: "Tedd Dillard" <tedd.dillard@xxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Thursday, March 29, 2018 9:42:47 AM
> Subject: Re: [TCML] Unexpected RSG phase shifter behavior
>
> Steve thank you for your quick response.
> It sounds like we are going down the same road except that you are farther
> along than I am and know more about what you are doing.
> My transformer is a 10 kva pole transformer, 14.4 kv/ 240v.
> I too made a current limiting ballast like Richie's, I used three golf cart
> battery charger I E cores with an adjustable air gap.
> I have four identical 120 volt 20 amp variacs mounted on a common shaft.
> Two in parallel feed one side of the transformer and two in parallel feed
> the other side thru the ballast.
> I am not done with building the controller but with the high side shorted
> on the transformer I have so far adjusted the ballast for 32 amps and I can
> put as much as 298 volts on the transformer.
> I still have the rest to build and am most concerned with the tank
> capacitor. I really want to build a flat plate capacitor but am seeing a
> lot of negative feed back on them.
> I am also planning on building a SRSG so am very interested in your issue.
> I went back and read your first post.
> You see no visually apparent effect in spark length from phase shift.
> You have verified that you do get effective phase shift, I am assuming that
> was done under no load conditions.
> The fact that you see no apparent change does not mean there is none.
> But I have trouble understanding how you could be changing the phase as
> much as you say and that it would have no apparent effect.
> There is no change in sound?
> I would question if the phase is really changing under load.
> And if it is actually changing and having no apparent effect it would
> suggest that the thing that should be affected by the change is not
> responding for some reason.
> That is why I suggest the caps being too small and since they are already
> fully charged with even the worst case phase setting there is no gain by
> varying it.
> I am of course not educated very well on the resonance issue but the
> explanations given explain why no improvement with phase shift may occur it
> seems likely that there would be some change.
> Teddy
>
>
> On Thu, Mar 29, 2018 at 12:07 AM, Steve White <steve.white1@xxxxxxxxx>
> wrote:
>
> > 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
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> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxxxxxxxxxx
> > https://www.pupman.com/mailman/listinfo/tesla
> >
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