Re: New Coil/RSG Annoyance

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 4/19/02 9:56:59 PM Eastern Daylight Time, tesla-at-pupman-dot-com
writes:

Winston,

I assume you modified an induction motor to make it sync,
by grinding or filing 2 flats onto the armature?  In any case,
you can easily tell if the motor is locking by observing it under
fluorescent light.  No special stobe is needed.  Make sure the
fluorescent light is the normal ballast type, not the electronic
high frequency type.  Simply put the motor onto a variac,
and vary the voltage while observing the rotor disc of the rotary.
You'll see a non-rotating pattern caused by the stobing effect.  
It can be difficult to see the pattern, if you're not used to seeing it.

At some voltage, the motor should lose lock, as you lower
the variac setting.  Then the pattern will begin to rotate.  You'll
also hear a hunting sound (unsteady sound), like the motor
is trying to lock.  At a higher setting, when the motor is locked,
as you vary the variac, the pattern will shift slightly as the
phase varies slightly with voltage.  If none of this is seen, then
the motor is most likely never locking.  

In any case, it should not be a mystery if the motor is locking.
It should either be locking or not, and the difference should
be clear, and non-debateable.  It may help to put a strip of
white or black tape across the rotor, to make it easier to see
if it's locking.  Often the tape is not needed.

cheers,
John


>
> .
>
>     My motor is a 3600 RPM Dayton 3/4 HP job.  The rotor is 10" in
> diameter, and has eight holes in it, four of which were used at the time
> for (attempted) 240 BPS operation.  I am pretty sure that the motor is
> phase locking.  I can't tell for sure, since I don't have a good strobe,
> but it worked OK (not great) on my big coil.
>
> Thanks,
> Winston