Re: making a motor synch?

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

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 6/1/03 5:20:23 PM Pacific Daylight Time, 
tesla-at-pupman-dot-com writes:
>David,
>
>If it's got a centrifugal switch inside, then it probably has a start
>winding and is not a split phase type.


John,

I don't think that there is a centrifugal switch in my motor. The
armature rotor doesn't have the centrifugal switch spring assembly
thingy on it.

< This type should work OK,
< if the rotor is not too heavy, and the spinning electrodes are not too
< large/heavy. A lot of folks have used
< the bench grinder motors and modified them, but of course they
< dont' have as much starting torque as a cap-start motor.

I took the motor back apart and ground the flats a little more.
I also tried taking the rotory disc completely off and the motor
does sound like it synchs now. It will start making that hunting
sound if I introduce much of a load to the motor while it's run-
ning though (like pinching the rotating shaft hard enough with
my fingers- watch out). When I put the rotor disc back on the
motor, it can't synch though (makes the wa-wa-wa hunting sound
even with 140 volts input). The disc is a 3/8" thick X 9" dia. lexan
disc with all 6 of its 3/8" X 2" long brass all-thread rotory elec-
trodes removed.

< What's the armature diameter and the width of the flat that
< you created?

< I agree with the Christoph that it's a good idea to try a larger
< run cap, and see if that makes it sync-lock.

< John

The armature diameter is 2" and the width of the flats is about
1 1/8". The run cap that I have is a mere 6 uFD. And that's
ashamed because of all of the x-tra caps that I have lying around
the shop, I don't have any run caps in the 5 to 50 uFD range :^(
All of my caps are either a lot larger (can crusher) or a lot smaller
(tesla coil or MO). I guess I'll have to look up USA Manufacturing's
web page. BTW, I think my bench grinder motor is supposed to be
1/3 HP but it sure doesn't seem to have that kind of power to me,
even before I ground the flats on the armature. I did have the motor
driving asynch two of the aforementioned 3/8" X 9" lexan disc with
the 6 each 3/8" X 2" long brass rotory electrodes on each disc and
it would take the motor 15 to 20 seconds to reach full RPMs after
the power was turned on. Of course the two disc w/ their accom-
panying electrodes is a pretty heavy load for a 3450 RPM, 1/3 HP
motor, I suppose.

Anyway do you think that a larger run cap would make the motor
synch better under load and if so how much larger should the run
capacitor be?

David Rieben