Servo's and Power supplies

Hello,

I am currently working on a power supply to drive 3 servo motors and have a couple of questions and would appreciate any help!

The motors I have are 600oz/in from camtronics, and are rated at 38vdc 12amps max.

1. I am looking at a toroidal transformer and in my price range I can reall only afford a 500va transformer. There are two I am looking at, a 25vac 20amp or a 30vac 14amp.

The 25vac will give me about 35vdc at 20a, and this is the one I am leaning toward. My question is will there be any downside to running my motors at 35vdc rather than 38volts or even higher? From what I can tell I will only lose rpm and the toqrue is in the amps, is this correct or am I way off?

Im not even sure if 20a will be enough to power all three motors I plan to do alot of 3d contouring. The machine I am retrofitting is an RF-45 mill drill and I am driving the head rather than the quill, it is fitted with 5/8" ballscrews x & y and 1" ballscrew in the column. I am planning to connect x & y direct to the leadscrew and am undecided with the z axis. I am hoping to counter balance the head. Oh, and all leadscrews have .2in lead. Is the direct connection of the motors a bad idea? Its just more simple and cheap for me at the moment.

2. The second question I have is as to the protection of my power supply, firstly the capacitor I am planning to use is a 47000uf 40v not quite 20% higher voltage as geckodrive suggest, will this be a problem? And secondly I hear of bad things happening during deceleration of motors, how do I protect my power supply against this.
I am running 3x gecko 320's.

Thanks for any help, the list has been great reading and has helped me get this far!

Jason Cox.



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