Re: making a motor synch?

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

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

In a message dated 6/1/03 12:18:18 PM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:


>If available, a monitor can be set to a 60Hz refresh rate.  A TV's vertical
>scan rate (similar to a monitor's refresh rate) is about 60 Hz
>(59.something).  It would be hard to see a disc from the light of a monitor
>or TV, but your painted lexan disc would work quite well ;)  I once ran my
>coil out on a street corner in the city (remember that one, Boden? ;) ) and
>was able to see the elctrodes sweeping out about a 45 degree arc,
>presumably due to the sodium street lights.


Mark, all,

because the TV scan rate is not exactly 60Hz, the synced motor
pattern will rotate gradually, but is easy to see.  Although I often
mention that some
folks have difficulty seeing the sync-locked pattern under fluorescent
light, this does not mean that I don't recommend trying to see the
pattern under fluorescent light.  It just means that one must practice
until one masters the task, if they so desire.

To the fellow who heard the hunting sound (wa-wa-wa), did you
try feeding the motor with 140V from a variac?  Sometime this
gives enough voltage to lock the motor into sync.  Also, if the
spinning electrodes can easily be removed, this may permit
the motor to lock in sync, just so you'll be able to verify the locked
or un-locked condition.  The cardboard disc instead of the
heavy rotor is a good method too, to see if the motor can lock
with such a slight load.  Using flourescent light, only a blur will
be seen.  The key is whether the blur is locked or not.  One wants
to see a locked (non-rotating) blur, not a rotating blur, nor a
no-pattern blur.

I'm not sure how much metal should be removed for a 3450 rpm
motor to make it sync best.  When I modified my 1/10HP motor, I made
the flats about 1" wide on a 1.75" diameter armature rotor.  This
worked very well and may be  a good proportion to use.  I always
make the flats narrower than this when modifying a 1750 rpm motor
however, because the magnetic poles are smaller in this case.

John