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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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