Need help with servo power supply design

I would like some advice on how to calculate the proper power supply
size for a 3 motor servo system as specked below. I also have a post
from Mariss who has tried to help me.

Thanks

Wally



From: "Mariss Freimanis" <mariss92705@y...>
Date: Fri Feb 4, 2005 5:03 pm
Subject: Re: Servo power supply design


What I didn't see listed is the max continuous torque or rated motor
power in Watts.

1) If you have the rated output Watts, add it up for all your axis
motors and multiply the result by 1.33 (inverse of guessed at 75%
motor efficiency). That is the required power supply Watts. Amps
becomes Watts divided by supply Volts.

2) If you have only the max rated continuous torque, multiply it by
the motor's rated no-load RPM and divide the result by 1351. That
will be the Watts needed from the supply for that motor. Again, Amps
becomes Watts divided by supply Volts.

Mariss

--- In geckodrive@yahoogroups.com, "cnc_4_me" <mrcompute@g...> wrote:
>
> Mariss, could you give some advice on power supply design for a
servo
> system. If we follow your power supply document it seems to call
> for a huge transformer. For the servo below it needs 20 amps at 60
> vdc. If we have 3 of these we need 60 amps at 67% (67% per your
> pdf). This is 40 amps DC at 60 volts…Next the actual current draw
> from the transformer using a bridge rectifier and capacitor will be
> 1.8 x 40 amps = 72 amps.
> 72 amps AC at 45 volts AC = 3240 watts.
>
> Am I missing anything…..
>
>
> Torque constant: 44oz-in/amp
> Voltage constant: 32.5v/1000 rmp
> Peak torque: 600 oz-in, or 37.5 in-lb
> Nominal voltage: 40vdc
> Maximum voltage: 60vdc
> Demagnetization current: >20amps
> Terminal resistance 2.60 ohm
> Max rpm at 50vdc is about 1200 rpm
> No-load current <.51 amp
> Armature inertia .09oz-in-sec^2
> 4 bolt holes in face for easy mounting.
>
>
> Wally