At 07:49 PM 8/6/01 -0600, you wrote:

>If speed is a function of voltage, and torque is a function of current, it
>would seem that what is needed is a way to provide a relatively high
>(average?) current at a relatively low (average?) voltage.  I guess what my
>question boils down to is whether there is a way to accomplish this with PWM
>techniques, or by some other magical means I can't presently imagine.

Current is a function of voltage - back EMF , so the current naturally
goes up at any given voltage if the motor slows below it's no-load speed.
If you schlep full voltage onto a motor that is stopped, it draws the
maximum current (LRA = Locked Rotor Amperes) (well, ignoring the case where
you "plug" the motor by hitting it with full voltage when it is running
*backward*.)

By measuring the current you can adjust the PWM duty cycle up to maintain
a fairly constant speed for any given voltage. This is commonly done.

Best regards,

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