Confirming PSU spec for steppers.

[Rogue]

Yes it's always better to match current to motor ratings but not go higher. The only margin you want to leave is on the voltage but it's also always better if the drives are not max'd out on current IE max current setting = motor current so the drives not working flat out.!

That answers that question, I should have waited another minute or two before replying! There's approximately 10V difference between the transformer output and the driver max input which should hopefully be fine.

[JAZZCNC]

That answers that question, I should have waited another minute or two before replying! There's approximately 10V difference between the transformer output and the driver max input which should hopefully be fine.

Yes 10V will be fine and the fact your using toroidal transformer helps further still because the caps will absorb back EMF better.

[Jonathan]

Hi Jonathan, thanks for chipping in again. I'm still aiming to finish this before you finish at Uni so I'll need you to work towards a PhD, should give me enough time.

That's the plan, however at work they seem to want me to do the PhD whilst working them, in which case you've only got a year left!

My question was whether it's better to run the steppers at their max or give them a bit of a margin. If your answer still applies (which logic suggests it does) then it seems reasonable to set the drivers for a little under 4.2A.

Yes my answer does still apply. As you increase the current in the motor windings, the copper losses increase by the square of the current, so the motor will get hotter. The degradation of the insulation on the motor windings is dependent on the temperature, as with most chemical reactions, so according to the Arrhenius equation we can say (very approximately) that if the motors run 10° hotter, their lifetime will be halved (assuming they fail due to insulation breakdown). This sounds bad, but we have to put it in perspective - if the motors last 20 years then halving this to 10 years probably isn't a big deal.
I'd set the driver current as near as you can to the motor rating without exceeding it. You might be able to go lower, but I think it's better to ensure the machine will not stall by having a good safety margin, rather than worrying about the lifetime of the motors.

Going back to me previous point about the power supply, I just ran the simulation again but this time with both configurations. The first graph is with the windings connected in parallel on the DC side and the second graph has them connected in parallel before the rectifier:



I realise that there's not much point discussing this further, but it's interesting to note that the waveforms do look slightly better for the DC coupled version. There's still not much in it.

[m.marino]

AM882's are an excellent bit of kit and really are easy to use once you get around the chinese strange way of setting up the software for programing the drives. I use them and they really do make things run very very smoothly. -Michael

[Rogue]

That's the plan, however at work they seem to want me to do the PhD whilst working them, in which case you've only got a year left!

Glad to hear it, it's not that common these days to get your foot in the door of a good job straight out of Uni. Make the most of it and don't forget us whilst you're busy making money!

AM882's are an excellent bit of kit and really are easy to use once you get around the chinese strange way of setting up the software for programing the drives. I use them and they really do make things run very very smoothly. -Michael

From reading around a bit more I think I'm sold on the AM882 drivers. Currently got 3 of them (+ a lead) sitting in my basket at Zapp. Wisdom dictates that I don't pull the trigger until the end of the month, but my trigger finger is getting fairly itchy at this stage

[JAZZCNC]

From reading around a bit more I think I'm sold on the AM882 drivers. Currently got 3 of them (+ a lead) sitting in my basket at Zapp. Wisdom dictates that I don't pull the trigger until the end of the month, but my trigger finger is getting fairly itchy at this stage

Do it because sure has Egg's is egg's they'll be out of stock when you want them.! . . PUSH THE BUTTON!!

[Rogue]

Do it because sure has Egg's is egg's they'll be out of stock when you want them.! . . PUSH THE BUTTON!!

Don't tempt me! I really, really shouldn't. If the drivers are out of stock then I can always move the ballscrew purchase forward by a month.

[Swarfing]

House prices are rising, everything else will follow?