CAD CAM EDM DRO - Yahoo Group Archive

Stepper Motor Power Calculations

Posted by Phil Mattison
on 2006-01-22 12:01:51 UTC
Hi, I'm new to this board so I've been watching for a couple of days, and it
looks like the discussion gets pretty technical, so I'll run this one up the
flagpole:

I recently built a stepper motor control box for PC parallel-port stepper
control using some motor controllers that incorporate PWM chopper-type
current regulators for the motor phases. The regulators operate at a range
of voltages, so I selected a power transformer within the voltage range of
the regulator with a current rating equal to the sum of the current
requirements of the motor coils. But I think I may have overkilled it using
this approach.

Now that I think of it maybe I should have calculated the power consumption
(watts) of the motors at maximum current, and used that to determine the
current rating of the transformer, since the motors run at a lower voltage
than the transformer supplies.

For example, if the motor coils are rated at 3 amps max, and the resistance
is 2 ohms, the coil will drop 6 volts when running at max current, which
means they are dissipating 18 watts. If I have four of them that's less than
80 watts total worst case. A transformer with a 20-volt secondary would
therefore need only supply 4 amps, not 12 as in the simple-minded approach.
Oh-well, live and learn.

I guess I was thinking the chopper acts like a linear voltage regulator, but
on reflection I think it acts more like a transformer, and so the power
calculations would apply. Has anyone seen a difinitive answer to this
question? Thanks,

--Phil M.

Discussion Thread

Phil Mattison 2006-01-22 12:01:51 UTC Stepper Motor Power Calculations caudlet 2006-01-22 13:54:49 UTC Re: Stepper Motor Power Calculations JanRwl@A... 2006-01-22 23:41:23 UTC Re: [CAD_CAM_EDM_DRO] Stepper Motor Power Calculations Phil Mattison 2006-01-23 07:53:09 UTC [CAD_CAM_EDM_DRO] Re: Stepper Motor Power Calculations caudlet 2006-01-23 09:08:24 UTC Re: Stepper Motor Power Calculations Phil Mattison 2006-01-23 16:13:08 UTC [CAD_CAM_EDM_DRO] Re: Stepper Motor Power Calculations Vlad Krupin 2006-01-23 16:33:13 UTC Re: [CAD_CAM_EDM_DRO] Re: Stepper Motor Power Calculations Phil Mattison 2006-01-23 17:43:51 UTC [CAD_CAM_EDM_DRO] Re: Stepper Motor Power Calculations Mariss Freimanis 2006-01-23 19:20:05 UTC Re: Stepper Motor Power Calculations Phil Mattison 2006-01-24 09:10:47 UTC Re: [CAD_CAM_EDM_DRO] Re: Stepper Motor Power Calculations Mariss Freimanis 2006-01-24 11:53:55 UTC Re: Stepper Motor Power Calculations