Dear Don,

From: Don Foreman

Message-ID:

I think the generators described on the website work by resonating the
main winding with capacitance.

I'd theorized this also.

Residual magnetism starts "pumping"
this parallel-resonant circuit to get the excitation current required.

Yep.

Each revolution gives the resonant circuit another nudge, like
synchronous pushes to a pendulum.

Since there are many poles, each 3600/225 = 1/32 revolution plus or minus
factor of two, that is it's got to be either 1/16 to 1/64 revolution pumps the
circuit.

Voltage would increase without
limit until something limits it -- probably magnetic saturation in the
iron.

I'll bet they have arranged that.

A fan motor may not work as well as some other induction motors
because some fan motors sometimes have pretty high resistance.

Over 100 ohms minor coil, around 35 ohms main coil IIRC. I can have it rewound
with silver magnet wire after I get it online..... The external coil _should_
have lower resistance than the equivalent internal (rotor) coil configuration.

If
it's "impedance protected" so it won't burn out when stalled, it may
not work well as a generator because that winding resistance may
spoil the Q of the resonant circuit.

I will recheck the namepate label, which gives the wiring configuration, for
"impedance protected". The web listing does not say.

The 10-1134 motor is such a
motor.

A fan motor or an impedance protected motor?

It sounds like your motor is a two-phase motor, the second phase being
produced with a capacitor.

Yes.

It's still an induction motor.

Oh, thank God. Buy you a latte someday?

I'd suggest that you
ignore the high-resistance winding, just put the cap in parallel with
the main winding.

Eureka! Of course. Good thing I bought two caps.

I'd suspect (and the website confirms) that this setup will not start
generating under load. You must rev it up and get the excitation
established before you connect a load.

Yes, shutdown under load will depole the rotor. However, my white LED signal
light from Dialight, donated by John Viselli when I provided the serial number
of the green traffic light I purchased on ebay under suspicious conditions,
shuts down at 80 VAC. It goes off line automatically. The perfect match.

You may need to experiment
with caps to get the amount of capacitance that resonates with your
motor. .

Or the driving speed.

Rev up the motor and vary capacitance while observing output
voltage, going for maximum.

Easier to affix the motor to the bicycle and crank at various speeds with known
capacitance. Looks like it's time to buy a cheap LCR meter, or get out the
scope.

Getting the speed right may be important. You need the speed to stay
fairly constant to stay near resonance.

Yes. I can drive the system backwards from the DC motor generator through the
derailer and chain under light loads. The ineria of the wheel will stablize the
speed. Dr. Majewski will provide 0-30 VDC for the DC motor generator.

If the motor's nominal speed
is 225 RPM, it's "synchronous" speed will be higher.

But 3600/16 = 225. So this must be nominal.

The difference
between synch speed and run speed is "slip" speed. To generate,
you'll want to run at synch + slip rather than synch - slip.


Yes, I understand this and will look in my EET 350 text for more.

You've given me enough information to get out of this funk and get on with it.
I'll report soon.

Thanks, Don.


Yours,

Doug Goncz ( ftp://users.aol.com/DGoncz/ )
Student member SAE for one year.
I love: Dona, Jeff, Kim, Mom, Neelix, Tasha, and Teri, alphabetically.
I drive: A double-step Thunderbolt with 657% range.