MP Toolman wrote:

Shunt wound or permanent magnet DC motors are inherently constant torque
devices because the magnetic field is constant at or below base speed.

Closer to constant speed devices. If the armature and power supply had
zero internal resistance speed would be constant independent of load. A
Variac and a bridge rectifier will do a pretty decent job for a power
feed.

http://www.metalworking.com/dropbox/_1999_retired_files/PWRFEED.TXT

Ted

You are correct, Ted, for a constant applied voltage this type of motor has
reasonably good speed regulation. I did not communicate very well, but I am
used to thinking about constant torque capability under variable speed. In the
case of a shunt wound or permanent magnet DC motor, the speed is proportional
to applied armature voltage and the motor is capable of producing constant
torque at any speed below base speed. Speed regulation with varying load is
quite good for a fixed armature voltage. The demagnetizing effect due to
armature reaction does effect speed regulation as does IR drop.

Mill