Re: Salient Pole Motor

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Winston,

If you basically followed the directions at:

http://hot-streamer-dot-com/TeslaCoils/Misc/syncmot.zip

The motor is in sync and it works fine :-))  People always want to "test"
the motors after the conversion and they spend all sorts of time doing
tests to "check" it.  So far, if the "test" shows the motor is not in sync,
the problem is with the test and not the motor.  There is about zero that
can go wrong with the motor (basic physics of iron there) but everything
seems to go wrong with the tests.  I have never heard of a converted motor
that did not work short of fire poring out of it ;-)  Strobe discs with
florescent lights seems to be pretty good but people sometimes get confused
by that too.  Finger presure on the shaft (be careful!!) just puts load on
the rotor which changes its sound considerably, but not it's speed.  Real
tachometers can be calibrated with your motor but they tend to be a
fraction of a percent off.  They are just analog meters unless they are
fancy crystal controlled ones.

So here is probably the best way to test it:

1.  Make a strobe disk out of cardboard that is 1/2 black and 1/2 white and
stick it on the motor shaft so it does not fly off (note that if it flys
off it make cut you!).

2.  Find a florescent light that does NOT have electronic ballast but the
old inductive brick ones.

3.  Run the motor off a variac and spin it up at full normal voltage.

4.  Watch the disk as you slowly turn the voltage down.  Soon the pattern
on the disk will start spinning as the motor looses sync.  This shows that
at full voltage the motor is in sync.

If you don't have a variac, you can probably just unplug it and see the
pattern spin out.


If you want to go all out, you can make a real sync motor stobe light:

http://hot-streamer-dot-com/TeslaCoils/Misc/RS-Strobe/RSStrobe.htm


Although it "sounds" easy to use a car timing light.  The inductive pickups
are hard to trigger from 60Hz AC and I gave up long ago on them.


The simplest way is just to assume it IS in sync because nothing can go
wrong :-))

Cheers,

	Terry






At 08:44 PM 3/2/2002 -0800, you wrote:
>Hi Everyone
>
>	It's me again.  Today I bought a surplus 3/4 HP, 3450 RPM, capacitor
>start  motor, with the intent of converting it to synchronous unit.  I
>ground the flats 180 degrees apart, and larger than I needed to, then
>tested the thing.  With no load, it appears to phase lock, but when I
>put any significant finger pressure on the shaft, it seems to come out
>of sync.  I used a car timing light for the test, using the AC line into
>the motor as the trigger.
>
>My questions are:
>
>1. Was using the timing light a problem?  I thought that since they are
>designed to trigger on a fast rise ignition pulse, smooth AC might make
>it trigger erraticly.  The flash from the light was not terribly smooth,
>varying in brightness, and (possibly) frequency.  I powered the timing
>light with a car battery, BTW (the way you're supposed to :-))
>
>2. What else could I use to more accurately tell if my motor works? 
>Would a light dimmer with a capacitor (ignition coil driver style) and
>xenon flash bulb work?
>
>Thanks,
>Winston
>