AC Stepper driver question

[BillStrahan]

When I first started messing with this stuff and made my own CNC conversion for the HF mini mill I quickly learned that higher voltage would allow higher stepping speeds. When I later upgraded a PM25 to CNC, I started with a 48 volt system and eventually ended up at 72 volts with DM860 drivers. It is smooth, fast, reliable. But it was a little pricey for the high current 72v power supply.

Now, I'm playing with a larger mill with large NEMA34 steppers and I just came across the DM2282T:

https://www.omc-stepperonline.com/di...per-motor.html

I intend to have a 220v spindle motor anyway, so this lets the whole system be 220v, and eliminates the need for a transformer for the DC to the stepper drivers. Three DM860T plus a good power supply would be about $350. Three of the DM2282T would be about $450, so only $100 more and a simpler system.

Am I missing something? I've seen commercial CNC systems that use stepper motors and use drivers similar to the DM860T and a power supply instead of these AC stepper drivers. I can't imagine why you wouldn't go the pure AC route, especially since it removes another point of failure, and sometimes a power supply failure kills the stepper drivers downstream from it as well!

Anyone have experience with these AC drivers? Anyone think I'm missing something as to why these aren't used more frequently? Would sure be nice to ditch the power supply and just wire drivers straight to the AC into the system.

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[joeavaerage]

Hi,
AC line input stepper drivers are well known and have been used extensively in the past. They all rely on a rectifier/capacitor input filter
followed by a buck regulator. The buck regulator adds cost and potential reliability issues and has, in the past, been restricted to
high value systems.

I use Vexta 5 phase steppers from a Japanese company, Oriental Motor Co., good quality but pricey. They have an extensive range
of 110VAC and 230VAC line input stepper drivers. I have three 230VAC input types. You are correct that you don't have to mess around
with another costly powersupply, but the real adavntage is that the regulated DC ouptput (of the buck reg) is about 150VDC. That means
the stepper driver proper has a 150VDC power supply, and my steppers SING. I commonly run them at 2400 rpm but they are still
quite happy at 3000rpm!.

As the price of high reliability power electronic parts has come down their use in AC line input devices has gone up.

Craig

[ferrret3238]

I use those drivers, only they're leadshine DM2282's. They work good driving my nema 42's on my plasma table. 240VAC in and just out to the stepper. Made wiring a lot simpler in the cabinet. Only trouble I had was when I was testing them I had a piece of steel fall on the cable going to the motor. It blew the drive up right now and I had to get another drive. Learned the hard way to keep cables up and out of the way.

[BillStrahan]

Thanks for feedback, guys! I'm sold. Since the current limit goes all the way down to 2.X amps, I'm probably going to do all my machines this way in the future.

[BillStrahan]

Did you wire you drivers directly to the mains? I've seen some people say that this should still go through a transformer, but I don't see what that should be the case.

[joeavaerage]

Did you wire you drivers directly to the mains? I've seen some people say that this should still go through a transformer, but I don't see what that should be the case.

Depending on te design of the driver you may or may not require a transformer.

My Vexta drives are designed to accept 230VAC direct. The AC input is rectifed and capacitor smoothed to 320VDC. That is reduced
to 150VDC by a buck regulator. Its entirely possible that it would work, that is produce 150VDC, with any AC input from 115VAC upwards.

You will have to be guided by the specifications of your drives.

Craig

[MileHiDude]

Hi
Am new to the forum, (at least as a poster).
I've had an all together different experience that I'd like to share.
I live in the mountain states and our grid is powered by Excel Energy.
Our grid consistently produces 120VAC Phase to ground, with a + or - allowance of 5%, (so a high of 126VAC phase to ground is permissible).
It is also my understanding that the system is typically preloaded (at 126VAC) in high use areas.
Using both phases as I do for all my 2-phase equipment (Mill, Lathe, CNC, etc), it is quite often that the power is at 250VAC or better.
I've incurred no damage of any sort until I installed and used the 2DM2280 Driver for a NEMA42 motor.
At first everything worked flawlessly as installed. However after 4-5 months the driver suddenly "poped" and has completely failed.
I've been in contact with the Amazon seller and they have been most accommodating, agreeing to a refund and some description modification on their
Amazon page regarding "overvoltage protection".
At this point I'm resolved to replace the driver but also replace the motor and install a motor driver assembly more capable of handling the power grid
in my area.
Additionally, I'm interested in finding a reduction transformer/regulator that will allow me to bring down the potential 252VAC to 220VAC.

Appreciate your suggestions