Re: Stepper motor voltage VS amps.

So for my example if I went with a 40-50V 3A power source it would be
correct?

Thanks for the great info.
It is a little brighter at my end of the tunnel.

Scott

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
> Miroslav Pejic wrote:
>
> >Hello Scott,
> >There is a light:
> >The driver regulates motor current in pulse manner. Every moment
when
> >current reaches 3 A, (actually, some more then 3 A) driver shut the
> >current off. Then, after little pause current get to zero. In this
> >moment driver supply the current again, and the process repeats,
with
> >frequency of 15 KHz or more. So, the average current is never
bigger
> >then 3 A, and this happens on 40-50 Volts.
> >Real power consumption is 3A * 40 V = 120 Watts.
> >
> >
> This is not correct. Real power consumption (for one winding)
would be
> 3 A * 40 V * fraction of time current is ON. Assuming the winding
draws
> 3 A at 2 V, then the duty cycle would be roughly 2/40 = 0.05, and so
> the power in would be 3 * 2 * .05 = 0.3 Watts. (Transistor and core
> losses in the motor would increase this somewhat.) This solution
> only holds for a stationary motor, and is the MINIMUM power draw
> when the motor is idle. Power consumption will rise dramatically
> as the motor speeds up.
>
> Also, note that PWM drivers will not let the current fall all the
way to
> zero before turning on again. That would cause excessive heating,
as well
> as reduce average winding current to 1/2 the rated value, reducing
torque.
> Most drivers turn the charging transistor on and off with a 10 - 15%
> proportional current band around the setpoint. Some others use the
> 'bang-bang' control algorithm, such that every sampling cycle, if
current
> is below the setpoint, charging is on for the full cycle, if
current is
> above
> the setpoint, then charging is off for the full cycle. But, all of
these
> follow the previous paragraph.
>
> Jon