More on Sigma Motors

Ian, I have a friend who used to work for Sigma on their Bridgeport
project. That's how I got this old catalog : ) He's given me some insight
in how these things are made and some great pointers on how to get a monster
motor for my Bridgeport.

These motors are rated for a maximum case temperature of 100C (212 F)that's
class B insulation in a 50C environment. That's a 50C temperature rise. So
all you have to worry about is heating effects. the similar case size motor
and rotor combination I find in the catalog is 20-2235D200-E2.6 with a 1.5
A 3.2 Ohm (? misprint ?) coil. The other motor listed is a 2.3 A 1.6 Ohm
coil. In either case you are talking less than 9 watts of heating in
unipolar.

Now I forgot but think your motor is 3.7 ohms and that translates to 1.6 A .
Find a multimeter and measure the resistance, or you can try the lower
current first and won't hurt anything.

Tom