Quote Originally Posted by AndyUK View Post
Well clearly I should have read ahead because you already know the method. Oh well, not editing it now. No just get a larger VA transformer. You probably need 1000VA based on your 13.3A current, but that seems a little high? Most of us have 500-600VA transformers when turning into DC, perhaps someone can shed more light on this.
Yes! Pretty please! The problem seems to be (assuming 1000VA is an issue- as I'm quite unqualified to judge) that 4-4.5nm steppers seem to be rated at 4-5A and with 4pcs that quickly adds up.

Quote Originally Posted by AndyUK View Post
I think most people tend to ignore Vmax and just give them as much as the drivers can manage, then limit the current on the drives so they don't burn. Typically with 3.2mH motors with a Vmax around 58V people use 68V (convenient toroidals are available). Basically I think you want the motors to be warm but not burny hot (demagnetisation occurs when they hit a certain temp).

The overvoltage protection you talk about is interesting though - what do the drives spec for the voltage?
For the record it also lists overcurrent protection. If you're after the input rating it's 20-70VAC and 30-100VDC. Is that what you were looking for?

When your're saying to max the voltage, shouldn't there be some room for the transformer to fluctuate (upwards) from the rated voltage? In this case the transformer outputs 70V which is also the max of the drives. Also regarding overheating, is it the wattage/VA that is the decisive factor or can voltage alone cause over heating? I'm thinking if higher than rated voltage is passed through a circuit but at lower than rated current (i.e. less than rated watts are being fed), shouldn't there then be "unused" resistance in the circuit to avoid overheating? If so, is higher than rated voltage more a question of the structural integrity of the circuit? Or does it maybe manifest in the same way in the end, i.e. burning components...? In the current case the transformer outputs 70V at 6A = 420VA and the drivers can take 70V at 8Apeak = 560VA. Even if I had 4 transformers in parallel and 4 drives in parallel, respectively, the total wattage would still not exceed that of the drives' capabilities. So getting back to what you said about maxing voltage and limiting current, as the drives can take more current than the transformer outputs, I should be on the safe side?

sorry, for the ramblings, my thinking hat came on while writing this...also b/c curious!