On Tue, 08 Jun 2010 08:51:50 -0700, Tim Wescott
wrote:


The servo amplifiers will be able to tolerate some sag -- they're
designed to work with power supplies that have considerable ripple, and
to them ripple and sag are the same thing. But they'll also have some
input voltage limit below which they're just not going to work right,
and that input voltage is going to be reached when you're asking for the
most torque from your motors.

Which brings up another function of the caps, which is to absorb
energy returned from the motor when it's decelerating a load. It's
possible to fault the amp by exceeding its input voltage limit if the
caps aren't large enough. A case like lowering a suspended load is
worse than decelerating a mill axis, but it's something to keep in
mind.

--
Ned Simmons