Choosing AC vs. DC for stepper motor drivers

I did quite a few general searches on google and this one on LinuxCNC:   

Your search ac vs dc supply voltage for stepper drivers did not match any topics.

So I figured I'd start a new topic.

I bought four Rteligent R86 stepper drivers because they easily exceeded my needs as I understand them. 

I will attach the Docs for the curious.

This driver offers the option of either AC (20-80v) or DC (24-100v)

Obviously if I went with AC I would need a transformer similar to this one:

www.digikey.com/en/products/detail/hammo...ng/166G80/270170It's listed as 115vac to 80vac Max-current 500 mA Max-power 40VA.

My question is what advantages / disadvantages does AC have over a 72v DC supply? 

The only thing that occurred to me was maybe smaller gauge wire or lower loss for longer supply cable runs vs DC. 

Neither seem important enough for them to include that as an option unless the driver itself prefers it and they don't mention anything on that topic in the documentation.So I'm wondering if anyone in the community has experience with the AC option on a stepper driver?

I used one of these 60v AC toroids for my  Rtelligent ECT86 drives

I had a couple of these custom  made for another project.

Toroids are generally preferred for steppers.
Often a toridal power supply for steppers will include a DC recifier.
This is unecessary if your drives accept AC and it also simplifies the wiring.

I'm not sure of the internal circuitry of the drives, but somewhere the voltage must be converted to DC to operate the steppers
converting AC to DC steps up by a factor of approximately 1.4 so this 60 volt gives around 84 volts.

Oh, and I forgot to say don't go to the maximum voltage. look for something in the 50-72 volt range so you don't push to the limits.

Thanks for the info!

I didn't mention it but I was thinking of using a Variact so I could adjust output voltage and use 110/220 if need be.

Since you have experience with this specific driver - What do you think?

Is is worth the extra $20x4? (3 axis dual y)

Oh, I forgot the cost of the variact which is likely ~$50-60.

Can't forget the little extra's.

Normally you get ac input drives for high voltage and no need for a psu. Just plug into mains.

At 80v this makes no real sense cause you'll need a tx. Just use a dc supply instead because internally all the drive is doing is converting your ac to dc.

resmond wrote:

Thanks for the info!

I didn't mention it but I was thinking of using a Variact so I could adjust output voltage and use 110/220 if need be.

Since you have experience with this specific driver - What do you think?

Is is worth the extra $20x4? (3 axis dual y)

No need. Just get one that is correcty tapped for 110v and 220v input. The one I showed has inputs for 110v and 240v. It did not cost me anymore.

That's why I asked!