Jeff Wisnia wrote:
Art Todesco wrote:
Well, if it always turns in one direction the food will tangle, so you
must
untangle ..... just kidding. Many gear-head motors that run on 110 AC,
have "shading rings" to set up the magnetic field so they always
rotate in the
same direction. These are 1 turn chunks of copper that will go
through and/or
around the steel laminations. I have noticed in the last few years,
many small
motors like that, don't have shading rings and will start in a random
direction.

What kind of motors do you think those are?

AFAIK, without shading rings a simple induction motor will not self
start. But, there are all sorts of small motor designs around now I
never encountered when I was a kid, just think about what's in a modern
automobile.

Perhaps they're using DC motors, two phase AC motors, or some kind of
stepper motor for those microwave turntables now, driven by a few
components on the appliance's circuit board.

Based on what Edwin said, I doubt that the starting direction is really
"random".

Jeff

I guess if it doesn't make any difference, like in a microwave
turntable, it makes
the motor $0.00001 cheaper. BTW, my microwave does the same thing.


I know my 4 year old GE microwave's turntable always rotates in the same
direction as my grandma's Victrola's, but it might be interesting for
the OP to run some tests or even, G-d forbid, RTFM and let us know if
it's really random.

Jeff
You're right. I even saw a motor with a
mechanical direction unit. If it went the
"wrong" way, it bounced off a ratchet
device and went the other way. But I
thought a small motor with a rotor would
self start. It's just the synchronous
ones that
wouldn't start by themselves unless
something it added. I know old (very
old) clocks
had to be "spun" to get them going.
They too, would go either way. But,
as you stated, it's probablythe way the
whole thing was designed.