Reducing the space in my garage.

[JAZZCNC]

Could someone please let me know what the answer is here - I just need to have these thing clear in my mind as all the calculations can be a bit confusing!

I've mentioned the ideal voltage to run these motors at and why in 2 post's now but you seem not be listening.! . . . One more time then with little more WHY.!!

The Gecko site suggestion is working on the safe side but in practice the modern hybrid stepper motors we use and in particular the low inductance 3/4Nm available to us easily handle 70Vdc. Combine this with Modern Digital drives which handle current, motor heating and resonance much more efficiently then performance is greatly increased in several ways. More speed, more torque at higher speeds and smoother running motors.

Regards the transformer then all you really need is to size it so it outputs the voltage required and some extra amps for overhead. The volts are the main thing to concentrate on because if you go to high here you can blow the drives if tolerence peaks higher than there max rating. This is why 80V drives running 68Volts is safe.
You can get away with 500Va and 2x50V wired parallel or 2x25v wired in series with 3 x 4.2a motors without any troubles and I've run these with 4 motors in past without any issues but the 625va is the better option with 4 motors as it gives higher safety margin for say 4th axis.

Reason you can do this because all 4 motors are never pulling full amps at same time and the way the unregulated transformer/drives work they only pull amps on half the PWM cycle so don't draw the full rating of the motor. Combine this together and you can get away with Transformer Amps 60% of total motor amps but you still need the voltage to get the speed/torque from steppers.

Like irving says you can get away with much less caps and using 3 x 4700uf wired in parallel is my prefered way as they are cheaper, easier to find and lower ripple I believe.!

Regards the Bob then not sure what your meaning because voltage is very important to the BOB.? . . Feed it more than it's I/O can handle and you'll fry it every time, infact on the cheaper Bob's like the Oppb v3 you'll drasticly shorten it's life if you run any where near it's limit.

99.9% of BOB's will have voltage requirement or voltage range to operate and run things like Opto's and relays etc. The Motor output side of a Controller is often 5v logic and all the BOB does is pass it thru or in some cases will filter and boost the signal to 5V if lower.
Only the standard I/O side can vary regards voltage/current and even then your BOB will have a limit it can handle. The cheaper BOB's will restrict you to 5V others will be 24 or 30Vdc.
Again in practice your better running 24V thru I/O and the safety system limits Etc to help resist any noise interference.

DONT buy a cheap BOB they are very important and seriously under rated in how they can negatively affect the machine performance and shorten the life expectancy of your Hair.!!

Hope this helps.!