We are working on a (PIC driven) application which uses a 90 Volt DC-PM
motor. In some circumstances we want to lower the speed to about half of its
full-scale value, but we still need the torque we get out of the motor at
its full speed. Of course we can lower the speed by lowering the DC drive
voltage, but it seems that the torque also falls off proportionately to the
lowered voltage.  Does anyone know of a control technique (PWM maybe?) that
allows lowering the speed while maintaining the torque?  I am obviously not
a motor expert.  Am I trying to break the laws of physics here?  Any
suggestions welcome. Thanks very much,
        Foster

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