[KenoSlim]

Hi Folks,

I'm hoping someone can double check my math here concerning a power supply. So far I am the epitome of bad buys and costly mistakes in the CNC world. I should write a "Don't follow my lead" book.

Here's what I have and what I have come up with. I have two Nema 34's at 2.0 volts, 6 amps each running on my x and y axis. 1/2" 1-8 4 start turn direct drive. I have a Nema 23 at 2.8 amps and 3.64 volts on my z axis with 1/2" 1-10 single start. I don't want my power supply to the drivers to go much over 40 volts although I can go 50 tops.

Averaging all I come up with 2.54 stepper volts average, times 20 equalling 51 volts. I want the driver supply roughly at 40 volts so divided by 1.4 I get 28.6 VAC. Averaging stepper amps I have 9.91 amps, times 20 to get 198.2VA. My calculations show I need a 28,000 capacitor.

I have rounded up a 250VA 30V+30V Toroidal Transformer, two 26k uf 75 volt capacitors and a 15amp 240V rectifier.

Am I going up in smoke again or am I on the right track? I do have a switching power supply I can use on the z axis if needed. I prefer to have things all linear however.

Thanks ahead of time!

Slim

[joshua221]

When you raise V x 20, I should / 20. Basically your watts stay the same. P=I x V

[CoAMarcus]

Slim,

If you were to get an Antek AN3232 transformer it will do you just fine. It is 32V and 9.3A, which should be enough for you to run your machine comfortably. Put a 22000uF capacitor on there with a GBPC3504 bridge rectifier found below. I just built this power supply last week and it works very well. Here are a bunch of links to the parts you need:

Bridge Rectifier:

http://search.digikey.com/scripts/dk...=GBPC3504DI-ND

Capacitor:

http://search.digikey.com/scripts/dk...name=P10029-ND

Transformer:

http://antekinc.com/AN-3232.pdf

What is the inductance rating of your motors?

Marcus

[jharts1]

i never saw your cap calculation, but iget the feel'n your truy'n to usea static power supply to do what rotory supply will do > sorry i'm no help,,,hartmann,

[rgammage]

You have two Nema 34's at 2.0 volts, 6 amps and a Nema 23 at 2.8 amps and 3.64 volts so lets take a different view ........

A motor rated at 2v and 6A taking power from a 40v power supply must do so only 5% of the time else there will be smoke! The 23 will take current for nearer 10% of the time ...... averaging volts and/or amps has no relevance.

The 34s take 12VA each and the 23 about 10VA so 34VA (12+12+10) total meaning the power supply MUST be capable of giving at least 34VA ......... or 1A at 40V! Any more capacity than this will give you resilience .... double or quadruple the current would be good for safety and so all axis could take their few percentages at the same time.

What you propose is over-rated by large factor ..... it will, of course, work, just cost more!

I hope this makes sense.

Richard

[KenoSlim]

Hi Guy's,

Figures I had a math error or two, Marcus found a better buy on a transformer than me and I'm way overkill on the set-up. So far no smoke? That's a good thing. If there is smoke you guy's just might hear of a mushroom cloud going up over southern Oregon from my frustration.

Slim