Re: [CAD_CAM_EDM_DRO] Re: Servo Motors....?

baccus61 wrote:

> Hi Jon
> Thank you for the reply. Made a big mistake on the encoders, didn't
> I. I guess I should be reading these threads a bit more closely and
> then I may actually learn something.
> If they are no good then I will use them for something else like a
> clothes line retractor or something equally rewarding but I really
> appreciate the help as it saves a lot of stuffing about in the dark.
> Just one query tho', How would I go about finding the peak current.

Without a lot of equipment, it is a bit difficult to detect this in a
"non-destuctive testing" way. In theory, the magnets should show
some fading of their field before they are demagnetized. By carefully
graphing the torque per amp curve, when you see the beginning of
the "knee" of the curve, stop right there. I've never tried this, so
I can't say you can get away with it. The destructive testing way
is to try increasing currents and then check the motor at lower
current. When the test at lower current shows a change in
motor characteristics, the last high current used was too much.
Oops, scratch one motor. This may be complicated due to the
magnets being easier to harm at higher temperatures.

Some motors designed for severe motion control use have enormous
peak reserve (difference between cont and peak rating) and some
have a much smaller one. cheap, alnico magnet motors have a smaller
reserve, generally. Most I have seen seem to have about a 4:1
difference between cont. and peak, but you can't count on it for
any particular motor.

Jon