Are DC servo motors linear?

[Eric R Snow]

I know the subject doesn't say it all. I would like to compare some DC
servo motors without having to mount them each on the machine. I have
figured out how to apply an equal load, measure rpm, measure voltage
and amperage. Because of the difference in the motor shafts and mounts
it is easier to measure these off the machine. So if the motors are
tested at a lower than normal voltage and amperage do the results
scale up easily?
Thanks,
Eric R Snow

 

[Larry Brasfield]

"Eric R Snow" <etpm@whidbey.com> wrote in message
news:02ir219d249gqn8or4dj46jv3r49u0aqse@4ax.com...

I know the subject doesn't say it all. I would like to compare some DC
servo motors without having to mount them each on the machine. I have
figured out how to apply an equal load, measure rpm, measure voltage
and amperage. Because of the difference in the motor shafts and mounts
it is easier to measure these off the machine. So if the motors are
tested at a lower than normal voltage and amperage do the results
scale up easily?

If you use the motors within their ratings, they
are linear for most purposes, neglecting the
stationary friction and brush friction. So if
your standalone measurements are done at
sufficient speed to dwarf those effects, they
will scale without any great surprises.

As for "scale up easily", I presume you can
use a calculator if your arithmetic skills are
not sufficient to easily perform multiplication.

Thanks,
Eric R Snow
--

--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[Eric R Snow]

On Tue, 8 Mar 2005 09:52:25 -0800, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

"Eric R Snow" <etpm@whidbey.com> wrote in message
news:02ir219d249gqn8or4dj46jv3r49u0aqse@4ax.com...
I know the subject doesn't say it all. I would like to compare some DC
servo motors without having to mount them each on the machine. I have
figured out how to apply an equal load, measure rpm, measure voltage
and amperage. Because of the difference in the motor shafts and mounts
it is easier to measure these off the machine. So if the motors are
tested at a lower than normal voltage and amperage do the results
scale up easily?

If you use the motors within their ratings, they
are linear for most purposes, neglecting the
stationary friction and brush friction. So if
your standalone measurements are done at
sufficient speed to dwarf those effects, they
will scale without any great surprises.

As for "scale up easily", I presume you can
use a calculator if your arithmetic skills are
not sufficient to easily perform multiplication.

Thanks,
Eric R Snow
Thanks for the reply Larry. I think I remember enough math. I can

still make change calculations than the checkers at the store. But
that's not saying much...
Eric