In a message dated 4/13/05 6:30:54 PM Eastern Daylight Time,
tesla@xxxxxxxxxx writes:
How much do you recommend one should mill off of a typical motor? This
effectively makes this a salient pole motor...sort of. For example, I am
using a 1/2hp, 230V,4-pole,1750 RPM motor which I start at about 280V so
it can "Lock-in" and then I reduce the voltage through time delay to
240V...If I leave the voltage high, the current input exceeds the
nameplate rating and the motor runs excessively hot. What luck has
anyone out there had? Suggestions for milling depth would be helpful,
and appreciated, since I'm getting ready to mill down another armature
or two.
Henry,
For 1750rpm motors I grind 4 flats that are about 1/4 the armature
diameter. For example if the armature is 3" dia, I make each flat
about 3/4" wide.
For 3450 rpm motors, I grind 2 flats that are about 1/3rd the
armature diameter. For example a 3" armature would get
1" flats. Maybe the flats should still be 3/4" wide like the
1750rpm motor, I don't know. There are various opinions.
In general milling off more metal makes the motor run hotter.
Some folks use the concept of making the flats match the
width of the "dead poles" of the motor (the poles that have
no windings on them). However I think this method doesn't
always work that well especially for smaller motors that are
2HP or less. So I use the proportional methods described
above.
My phase shifter circuit can be used to shift the phase
remotely.
http://hometown.aol.com/futuret/page3.html
Cheers,
John Freau