Re: SRSG questions

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

Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

At 16:10 22/04/03 -0600, you wrote:
>Original poster: "Christoph Bohr by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <cb-at-luebke-lands.de>
>
>Hi!
>
>I think we have a  similar problem....

This is what I learned from the few university classes on electrical 
machines that I managed to stay awake through.

Some motors are more suited to sync conversion by grinding the rotor than 
others. The best kind of motor is a 4-pole capacitor-run motor. You can 
identify this kind because it has a motor run capacitor bolted to the 
outside and it runs about 1450rpm (50Hz) or 1750rpm (60Hz) You grind 4 
flats on the rotor and it should run synchronous at 1500/1800 rpm. My cheap 
$40 Chinese drill press has one of these, I would have converted it long 
ago, but I find the drill press too useful to do without.

Other kinds work less well. 2-pole types (rated around 2850/3450rpm) need 
only 2 flats on the rotor and the flats have to be bigger with all the 
torque problems that entails. Motors without a run capacitor don't do too 
good either.

The small shaded-pole motors you find in microwave oven fans etc don't seem 
to work at all. Some fairly large motors (100W) are actually shaded-pole, 
they can be identified by the copper shading rings built into the stator.

Steve C.