Stepper Motors and Power Supplies

Thanks again Todd.
PCW has pointed out that Leadshine shows +36VDC minimum in its summary table - the manual we received with the (secondhand) kit shows +24VDC minimum and i think whoever sourced the kit took this to be adequate.
george4657 has given me an explanation of why 24v will not adequately drive the motors and this has been confirmed today by getting the software and driver settings sufficiently correct to turn one motor briefly before the driver faults and shuts down.
omc-stepperonline sells kits with similar motors (but 5A rather than 6A) and supplies +60VDC 5.9A power supply for each motor. This may be the best way forward for us, although the current rating is cutting it rather fine. Probably a $30 investment to try getting one motor fully operational is worthwhile.
It seems that almost all the kit suppliers use switch mode regulated supplies, probably because they are relatively cheap and in ready supply. I looked into unregulated power supplies here in Australia and could really only find commercial units with high price tags. Pricing components to construct a suitable supply was similarly high.

If you take the time to read some of the gecko docs there is some relevant stuff. I seem to remember reading there that doubling the volts quadruples the torque or was that 10 x ? I run 2.8 to 3 amp steppers on a 48 volt power supply. The maximum current my drives can handle is 3.5 amps.When I first played with steppers, I worked with small nema 23 motor and a 19 volt power supply. This was a big fail with missing steps and I bought a larger motor and a 48 volt power supply based on data on the gecko site. Once I replaced the power supply, I never bothered to replace the stepper motor as it worked fine then.

So you have 3 x 6 amp motors = 18 amps.The other thing I learnt on the gecko site was that the power suppply could be overrated by 40%. So that means you need about 13 amps of power. With your larger motors, pushing the voltage higher is quite justifiable and many steppers run at 80 volts which I've seen is a common standard.

I am also in Australia and I use Meanwell switch mode power supplies. I think my total draw is about 12-13 amps so I'm running a 10 amp supply. I know there are some formulas out there to determine voltage from stepper specs but I've never bothered with the maths involved. I think most of us are like that, we just know what to do from experiments, failures or experience.

Best way to go is with unregulated PSU

www.geckodrive.com/gecko/images/cms_files/images/SMBFig15.jpg

Suitable transformer + bridge rectifier + Cap

Thanks I think we have been looking at Meanwell but not sure where it was from and I now note from their site that the largest suitable supply is 48V, which may suit our needs.

Thanks I have read the information there and priced components which turn out to be well beyond our price range.

Which is why Gecko and Techno say to use an unregulated power supply. Its a shame Jaycar no longer sells bare transformers.

Yes it certainly is a shame!
I guess ideally we would build a 1200W (80VDC 15A) unregulated supply to service all three drivers and motors.
After the fact, our application probably only requires Nema 23's or 24's Since we have 3 matched drivers and motors, and an unmatched power supply, it now seems prudent to replace the power supply with something adequate. The alternative, which is actively being discussed here, is to replace the whole kit. My personal preference is to just replace the power supply. Providing a separate power supply for each driver/motor pair would still probably be cheaper than replacing the whole kit with smaller motors but the decision is up to the team (in which I am a junior member).

If your max voltage is 80VDC you better keep supply output a bit lower say 68-72VDC to avoid problems.
www.geckodrive.com/support/step-motor-basics.html

Thank you very much.
We are currently thinking of 60V as this seems the most readily available option and sadly it will also probably be a regulated switch mode. It also seems that the most affordable option will also be rated at about 6A.
Am I right in thinking that we would therefore need at least two power supplies if we are restricted to 6A since they will be wired in parallel and therefore the current drawn will be additive? Am I also right in thinking that the Z-axis will have the least work to do and will contribute less to the overall average current load?

Personally I would say it is a big NO-NO to do like that with regulated PSU's.

Is it really that hard to get simple transformers in Australia?