RE: [CAD_CAM_EDM_DRO] Transformers

Hi John

Just a couple thoughts...

If 20 amps is your maximum peak current per motor you would certainly
want to have that capability to prevent nuisance tripping in full
accel 3-d diagonal moves.

However, depending on the machine, average current requirements will
probably
be much less. In my large low friction router avearage cureent is less than
one quarter
the peak capability.

So I rate the transformer accordingly. The supply capacitor can deliver the
full current for short periods just fine...like a fast ramp up or ramp down.
I can calculate the cap size requirements but I must know a bit about the
machine dynamics.

One other thought I would offer...if individual motors are fused and only
one
fuse blows, the others will perhaps keep going resulting in an unforseen
path
and a possible crash scenario. The estop system must be such that if any one
axis
Malfunctions all axes stop. A stop on following error or similar system can
do this.

As far as transformers for UK use I am not sure. Custom toroid kits with a
pre-wound primary
and customer wound secondary (about 1 volt per turn) are commonly available.

Les

Leslie M.Watts
L M Watts Furniture
Tiger Georgia
(706) 212-0242

Main page:
http://www.lmwatts.com
Engineering:
http://www.lmwatts.com/shop.html
Cnc surplus for sale:
http://www.lmwatts.com/forsale.html
Carved signs:
http://www.lmwatts.com/signwp.html


-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com]On Behalf Of John Stevenson
Sent: Sunday, April 24, 2005 4:18 PM
To: CAD_CAM_EDM_DRO@...
Subject: [CAD_CAM_EDM_DRO] Transformers



Looking for a power supply to run three servo motors rated at 100 volts and
20 amps.
I know I will need a 65 to 68 volt AC output to finish up with just below
100 volts as smoothed DC but what vA will the transformer have to be?
It looks as if you need 3 x 20 but not all motors will be running at once
and at full power.
Is there a formula for deciding this ?

Last question what size fuse will be needed for each seperate motor ?

John S.