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RE: [TCML] Questions on the Freau SRSG Phase Controller
Aric,
I do not think it is helpful to quote actual amounts really, as it so much
depends on the motor. It seems from my limited experience with this subject
that the bigger the motor (power wise) the more capacitance is needed.
Dependant on where your rotor is located on the shaft initially you do not
really need as much as 45 degrees shift anyway, what you have should do fine
provided the rotor is roughly in place already. I find it best to have the
rotor positioned on its shaft such that without any phase control whatsoever
the electrodes align at the top of the mains sine wave. This is easily done
with the scope method, but I would imagine with your way the best option is
visually look at the spinning rotor whilst illuminated by the LED's. It
should then align. If not, move the rotor on the shaft. You then have the
starting position to work from initially and the 45 degrees shift you have
so far would then be fine. When you run the SRSG, you can clearly hear from
the noise that you have the sweet spot.
John said the other day that apparently you don't need to have an actual
voltage rise for it to work. (I learnt something there as well)
With both my SRSG's, I found they start much easier if they have no phase
adjustment being used initially at start up. I then adjust the phase and
power sequentially once the coil is running. This is the reason I have my
rotor align with the peak of the sine wave initially.
Regards
Phil
www.hvtesla.com
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of A Rothman
Sent: 24 September 2010 03:57
To: Tesla Coil Mailing List
Subject: Re: [TCML] Questions on the Freau SRSG Phase Controller
The line-power LED I described works reasonably well. I have tried
capacitances up to 155uF so far, and am unable to exceed about 45 degrees
before losing lock. I never see a resonant rise in the voltage across the
motor. Has anyone used 1/2 HP motor, 3600 RPM with John's phase controller?
What capacitance did you find to be ideal?
Aric
On Wed, Sep 22, 2010 at 7:25 PM, Phil Tuck <phil@xxxxxxxxxxx> wrote:
> I have done a YouTube video a while back using much the same method as
> Gary, but with a phototransistor and infrared. I used a Schmitt
> trigger, which unfortunately meant you only got a small blip from the
> sensor, but it can clearly be seen being moved against the mains sine
> wave as I manipulate the phase control.
>
> http://www.youtube.com/watch?v=Wp8felW_BgQ
>
> Also a longer version. The trace from the sensor is much clearer in
> this second one.
>
> http://www.youtube.com/watch?v=Vd3tjmEk3aQ
>
> Great circuit John!
>
> Phil
>
>
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Gary Lau
> Sent: 22 September 2010 22:28
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Questions on the Freau SRSG Phase Controller
>
> For testing the phase-shifting behavior, I've found the easiest thing
> is, assuming you have a scope, tape a small magnet to the motor shaft.
> Place a pickup coil (something with maybe a couple hundred turns)
> beside the magnet and connect the coil leads to the scope input. Set
> the scope sync to "Line"
> so the sweep is triggered by the mains phase. When the motor is
> running, the pulse train generated by the magnet sweeping past the
> coil should shift as you vary the phase-shift Variac.
>
> Regards, Gary Lau
> MA, USA
>
> On Tue, Sep 21, 2010 at 8:03 PM, A Rothman <canihazpolepig@xxxxxxxxx>
> wrote:
>
> > John,
> >
> > Yes, it's me, Aric. I've been off the list for a while, and out of
> > coiling. I've decided to dust off some half-finished aspects of my
> > old coil, and give it a go again. This includes the SRSG phase
> > control, and a 4-MOT stack to replace a 15K/120mA NST supply.
> >
> > I wired-up a high-intensity white LED to a chain of Zener diodes, a
> > rectifier diode, and a current limiting resistor, to illuminate the
> > RSG rotor. The LED is illuminated for about 15% of each line cycle.
> > Peak current through the LED is 150mA. I'm hoping it will suffice
> > to allow me to view the phase-shifting behavior.
> >
> > Thank you for your help.
> >
> > Aric
> >
> > On Tue, Sep 21, 2010 at 4:22 PM, Futuret <futuret@xxxxxxx> wrote:
> >
> > > Aric?
> > >
> > > The setup may be OK as-is, if you're getting about 90 degrees of
> > electrical
> > > and mechanical phase shift before you lose sync lock as you keep
> > > turning the variac. If you're getting sufficient phase shift,
> > > then you can just put a stopper on the variac so you can't
> > > accidentally turn the knob too far and then use the system that
> > > way. Many folks have done that, and some of my setups are working
> > > that way. If you want to be able to obtain the full rotation of
> > > the variac, then you may need to add even more capacitance, but
> > > since you say the thobbing threshold occurs sooner with more
> > > capacitance, then perhaps more capacitance is *not* the answer.
> > > Usually it's possible to obtain some resonant rise across the
> > > motor when enough capacitance is used. It's not essential to have
> > > any resonant rise across the motor however. Usually without
> > > resonant rise, the motor loses sync lock
> > > (throbs) at some point as you rotate the variac knob, as you are
> > > indeed seeing. The bottom line is that the main thing is that
> > > you're obtaining enough phase shift. You can observe the
> > > mechanical phase shift under ballast-type fluorescent lights
> > > although some folks have trouble seeing the shifting pattern as
> > > you rotate the
> variac
> knob.
> > > The phase shift effect is easier to see using a neon bulb strobe
light.
> > >
> > > It's normal to see the voltage begin to decrease at some point
> > > along the variac knob's range. Usually a larger cap causes first
> > > a rise, then a decline in voltage. With a smaller cap, only a
> > > decline may be seen. None of it matters too much if you're
> > > getting enough phase shift, and provided you don't rotate the
> > > variac knob too far and lose sync while the TC is running.
> > >
> > > John
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: A Rothman <canihazpolepig@xxxxxxxxx>
> > > To: tesla@xxxxxxxxxx
> > > Sent: Tue, Sep 21, 2010 11:21 am
> > > Subject: [TCML] Questions on the Freau SRSG Phase Controller
> > >
> > >
> > > I have a SRSG, consisting of a 1/2 HP 3450 motor, modified for
> > synchronous
> > >
> > > operation via the usual grinding of flats in the rotor. The motor
> > > is
> > >
> > > equipped with a second winding, in lieu of a run or start cap, to
> > > provide
> > a
> > >
> > > second phase for starting purposes. It is switched out via a
> > > centripetal
> > >
> > > switch after the motor spins up.
> > >
> > >
> > >
> > > I have followed the standard schematic, but included a contactor
> > > which
> > >
> > > isolates the variac and the motor from the capacitor when power is
> > >
> > > withdrawn. I have increased the resonant capacitor value from
> > > 20uF to
> > >
> > > 105uF, in 5uF increments, and have not observed the resonant rise
> > > in voltage
> > >
> > > across the motor terminals. What I do observe is a monotonic
> > > decrease in
> > >
> > > that voltage, as the variac is adjusted from minimum inductance
> > > upward,
> > >
> > > until the motor speed starts to fluctuate, accompanied by an even
> > > steeper
> > >
> > > drop in voltage, but with 5-10V oscillation in unison with the
> > > motor's
> > >
> > > throbbing. As I increase the capacitance, the threshold at which
> > > the
> > >
> > > motor's throbbing starts seems to come sooner in the variac's
rotation.
> > >
> > >
> > >
> > > Help!
> > >
> > > _______________________________________________
> > >
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> > >
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> > >
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