According to what Gecko say and also what I recollect that Bob Campbell says it is just current per phase and not multiplied by amounts of phases.
 So for your 6.3A/phase it will be the 4.2A for parallel. There is certainly no harm in going bigger if you can pick up a transformer or PSU at the right price which is  bigger than you actually require.
Hood

There is certainly no harm in going bigger if you can pick up a transformer or PSU at the right price which is  bigger than you actually require.

Oh.  I thought the purpose of these calculations was to figure out the correct power supply required so you didn't go oversized.  If I can use a  power supply that has abit more amps yet still being at the proper voltage rating makes things abit easier.  I was looking at a few toroidal transformers to use in building of a power supply but their amperage output was abit higher then I figured I could use, but if I can safely go abit larger then it gives me a few more options to choose from.  I guess you adjust the max amperage that the motors get through the Gecko drives?

Cool.  Thanks,

Carl 

You probably know this but just thought I would mention anyway that the voltage of an AC transformer will need to be less than the DC output you want. When you rectify and smooth (with the capacitor) the AC you will get 1.4 times on the DC, eg 50V ac will give you 70Vdc.

Hood

But I am assuming I should not go over the max DC voltage rating of the lowest rated motor which is 65V taking in consideration back EMF?  The other motor can handle 75V.  If I select a Toroidal transformer of 45VAC which would give me 63VDC I should be ok or should I go with 40VAC giving me 56VDC to be safe?


Carl

Carl,
the voltage limit is determined by the max voltage of the GECKO drivers not the motors.
the power supply  AMPERAGE can be as high as you want as long as it is high enough to supply the max current of all the motors together.
remember you can not have too many AMPS AVAILABLE  but your VOLTAGE  must NOT be higher than the GECKO drivers can handle.
Chuck

Yes but the Gecko's max voltage is 90VDC and the one PacSci motor I got has max 65V on the label.  Wouldn't I have to be cautious not to go over that voltage or is that just a guidline the motor's manufacturer uses?  My other two motors can handle 75VDC according to the data sheet.  It gets abit confusing when different motor manufacturers use different ways to list their motor specs I find. 

The max of the Geckos is 80V and its best to really stay around 75V especially if your mains power can wander a bit.
 Where in the specs of the motors does it say a Max voltage, I have never seen that on the specs of the motors I have had but then again I have only had a few different kinds.
Hood

Ahhhh. Ok... Now do you take that Amperage value and multiply it by the number of phases?

For example. If my motor is rated at 6.3A per phase and I take 2/3 of that value, gives me 4.2A per phase in Biploar parallel but the motor has two phases so do I multiply 4.2 by 2 giving me 8.4A for that one motor? Is this correct or do I just take the 4.2A as my value for the one motor?

Only one phase of each motor is energized at any time, so no, you dont need 8.4 per motor, just the 4.2A.  At least that is how I have allways understood it.