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RE: [TCML] Questions on the Freau SRSG Phase Controller
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!
> >
> > _______________________________________________
> >
> > Tesla mailing list
> >
> > Tesla@xxxxxxxxxx
> >
> > http://www.pupman.com/mailman/listinfo/tesla
> >
> >
> >
> > _______________________________________________
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> > Tesla@xxxxxxxxxx
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> >
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