Re: [CAD_CAM_EDM_DRO] Re: What makes a motor a servo?

Mariss Freimanis wrote:

>The picture is not quite as rosy as painted in favor of DC brush-type
>PM servo motors. Consider this comparison between a NEMA-34 stepper
>and a NEMA-23 servo motor:
>
>1) Servo: 6,000 RPM rated load speed, 60 in-oz continuous rated
>torque. The max continuous torque is just that; no to be exceeded.
>

Why do manufacturers give a peak torque, if the max continuous must never
be exceeded? I know your servo drives do not have an RMS limit circuit,
and a lot of others (like mine) don't, either. So, there would be a certain
kind of "going out on a limb" to set the current limit above the max
continuous
rating. but, most servo motors have a peak torque (and current) that is
4 to 8 times greater than the max continuous rating.

If you insist on never exceeding the max continuous rating, you can't
burn up
the motors, but it will require you to use MUCH larger motors. For
instance,
the people using the ubiquitous Ametek motors (Camtronics, etc.) generally
cannot even break the static friction on the machine at the continuous
current
rating of the motor. IIRC, the continuous rating is 2 A, the peak is 12 A.

Jon