> 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,
>

Presumably you do mean torque and not power. Torque should be able to be
maintained with decreasing speed as noted by others but power, being the
product pf speed and torque, will decrease as you slow unless you increase
the torque.

What is your current doing as you reduce speed?




            Russell McMahon
            apptech@clear.net.nz

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