Stepper Motors and Power Supplies

We are constructing a CNC driven router and have the following hardware:
1 Sunpower switchmode power supply rated for 24v 20A;
1x 5-axis breakout board from Savebase together with its documentation;
3 x MA860H drivers including documentation which appears to have also come from Savebase as the wiring diagrams show both the aforementioned breakout board and the drivers;
3 x Nema 34 motors labelled 34H2120-60-4A but with no indication of the manufacturer and no accompanying documentation.

I have sourced documentation for Nema 34 FL34H2120-60-4A with specifications including 2 phase/1.8 degree step angle, holding torque of 1200 oz in., peak current 6A, resistance 0.5 ohm and inductance 6mH and (probably) 80VMax , 3.3V phase voltage.
Is it reasonable to assume that these specifications will apply to the motors that we have?

Established wisdom suggests that the power supply we have (24v 20A) is probably too small to drive the steppers but I cannot find any explanation of why such a power supply is unsuited.
Can someone please point me in the direction of such an explanation?
Some documentation on the web seems to indicate that the voltage rating of the power supply is not relevant provided that it can supply sufficient current. Is this correct? How does it relate to established wisdom that the voltage of the power supply should more closely align with the maximum voltage rating of the steppers?

Any advice would be greatly appreciated.
Paul

I would think you will want at least a 30 amp power supply if not closer to 40. and I would run the voltage at the maximum that the drivers are rated for (80v). My understanding is that the max voltage on a stepmotor name plate can be mostly ignored, what is important is the max current, and the drive limits that.

The docs I googled up on the MA860H list 36v as the minimum supply voltage, this and insufficient current rating are the reasons your 24v supply won't cut it. Also it's my understanding that switch mode supplies usually are not the best choice for motion control.

Thanks for this too Todd.
I will take your advice back to the group.
My question regarding "why" a 24V supply will not suffice remains something on which I should like further theoretical information, so i hope someone may eventually point me in the direction of something that explains it..

With the right driver a 24v supply may infact run those motors, although not at their peak capability. The motors inductance will significantly limit the max rpm you could achieve with them at that voltage, and may lead to problems with missed steps.

PS, I think those drivers can run off of AC input, so you'd only need a transformer to send 80v AC to them rather than find a big DC power supply. (the max voltage for DC is +110v)

What you call established wisdom is just plain wrong! Todd's wisdom is where you need to go. If your drivers can handle 80 volts, give them 80 volts. You are setting your setting yourself up to fail on 24 volts.

Thanks, Indeed Todd's wisdom is what i was referring to as "established wisdom".
What I should like to know is "technically why" 24 volts will fail?

Actually the Leadshine MA860H specs show 36V minimum AC voltage and 50V minimum DC voltage

Not sure why they have this limitation but even if they did happen to work at 24V,
you would be limited to about 1/4 of the speed capabilities of the motors/drives

technically why" 24 volts will fail?
Your motors are peak current 6A, resistance 0.5 ohm so 12 volts is all that is needed to hold motors in position.
The problem is to move the motors switch polarity back and forth. It takes time to do this as the inductance of the motor resists current low. The higher the voltage and the lower the inductance the faster the coils can switch polarity. At high speed the coil will not reach its peak of 6 amps prior to switching direction so average amps are down and torque is lost. The higher the voltage the higher the average amps and the higher peak speed is before power loss prevents moving.
Your motor supplier my be saying that 36/50 volts is the minimum to get a reasonable high speed not the minimum to work at all or it may be that their drivers are not designed to work at lower voltages.
.
Edit: 6A at .5 ohm = 3 volts required not 12

Thank you George.
That now makes sense. Almost every article I have seen prior to this has glossed over the explanation and gone on to talk about the disadvantages of too much voltage generating heat rather than additional torque.