Re: [CAD_CAM_EDM_DRO] How to test a servo motor without servo drive?

I think your worries are unwarranted. There is nothing wrong with applying
the full DC voltage to the motor assuming you stay within the motor's
nameplate volts rating. Just clamp it down :-). As soon as it begins to
spin up, it generates its own back-emf, opposing the heavy starting current,
and settles into a low load running current, probably around 10-15% of full
load current. This is entirely normal and acceptable. Also I don't remember
anything about damaging those permanent magnets built into the motor - not
likely to happen...where I believe this came about was rumor from the days
of those older generators common to most vehicles not so long ago, since
replaced by alternators. These generators used an electromagnet to do
exactly the same thing our permanent magnet motors do, generate a magnetic
field. They used an electromagnet to 1) save money and 2) to save weight.
The electromagnet would retain some residual magnetism after its first
startup (first time required "polarizing with a good shot of heavy DC
current directly thru the coil) and start generating after a shutdown, but
under some circumstances, one could lose that residual magentism, requiring
a repolarization. Not a problem with that heavy permanent magnet in your
servo drive.

Hard to believe all that motor/generator coursework at Penn State came to
some use :-)

Cheers

R. William Kichman, P.E.
Kichman Engineering Associates
103 Old Furnace Road
Cornwall, PA 17016-0643
tel/fax 717/270-0714

----- Original Message -----
From: "autom8_it" <engineer@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, August 09, 2003 2:15 AM
Subject: [CAD_CAM_EDM_DRO] How to test a servo motor without servo drive?


>
> I am doing a retrofit and I recieved my servo motors but I am still
> waiting for drives from Rutex. I would like to test the motors now
> and I am wondering if there is an easy way to do that without risk of
> damaging the motor?
>
> My guess is that a constant DC level will work but I would imagine
> that I would have to limit the current. It seems too simple to use
> ohms law and put in a series resistor?
>
>
> Thanks,
>
> John
>
>
>
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