Question for Mariss - Servo Motor Current

Hi Mariss,

I've just converted my BP clone from steppers (G210's) to servos
(G320's) and have confirmed as expected, that I need a bigger power
supply (PSU). Your white paper and most of the group's discussions have
been related to stepper motor current requirements - so I thought I'd
ask about PSU guidelines for servos. My motors are rated at 20 amps max
but I'm hoping I won't need a 60 amp power supply!

Setting the G320 current limit pots to max, I connected a 0.1 ohm 25W 1%
resistor (thanks, Digikey) in series with my existing PSU (65VDC 12
Amps, 15,000uF cap) and with my scope, measured the idle currect pulsing
to about 5 amps (for all three motors) during servo ticks. When I
started the mill running some 3 axis exercises, as I increased
accelerations and speeds to near desireable rates, I observed the load
current peaking to around 35 amps during a motor stop/reversal. The PSU
output voltage would drop way out of regulation (more than 10V) during
these peak loads and I observed the G320s would momentarily illuminate
their fault LED's. Short term I can run lower accelerations while I
beef up the PSU.

Clearly I can increase the capacitance by adding another 15,000uF cap,
but is the 2/3 current design rule (i.e. 40 amps) applicable for a servo
power supply design?

Cheers, Peter