DMM Servo drive faults

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Thor
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DMM Servo drive faults

Post by Thor » Wed Apr 07, 2021 10:52 am

I've been chasing this issue for a couple years and still have not figured it out.

Candcnc Command CNC setup sending step and dir signals to DMM Dyn 4 servo drives and 750 watt servos.

I keep getting Y2 motor faulting out, usually either overvoltage or Lost Phase.

I have installed a Line reactor on the power feeding the drives as recommended by DMM to help with noise. I have replaced the encoder cable 2x now with brand new cable from DMM. Only difference between Y2 and all the other motors (Y1, X, Z) is that it has a shorter cables as its closest to the energy chain and control cabinet.

The overvoltage error, (when this appears it can be all drives) seems to be due to the fact that the drives kick out at 250vac and my incoming power is at 247vac (converted to 3 phase though a phase perfect digital converter). Seems like if my cnc turning center or mill is running at the same time, on a spindle ramp up or down the voltage spikes to 250-251 vac and trips the drive or all drives in the plasma. Power company said they dont care unless incoming is over 252vac with nothing running in shop.

I'm out of ideas on how to address either issue. Do I need to install a transformer just to power the servo drives? What would I even find to change from 247 to 240 vac? On the encoder issue I have tried running the drive end of the cable through a ferrite core a couple wraps, doesn't seem to help. Only other thing I can think of is to completely separate the torch cable to a new energy chain by itself. I have tried to keep it off to one side of the current chain and the encoders to the other side but doesnt help much either.

And I still need to wire up a fault signal from the drives to Command Cnc, so I don't have to babysit it all the time to watch for the gantry to go wonky.

Maybe its the DMM stuff, as I have them on my press brake retrofit as well, and the back gauge will go nuts occasionally there as well like hunting for position, but that uses analog command with encoder feedback to controller. Ughh, I need someone that knows this stuff to come spend a week and fix it all for me lol..

Any ideas appreciated, though I have tried more than listed here as well to no avail.

beefy
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Re: DMM Servo drive faults

Post by beefy » Wed Apr 07, 2021 4:49 pm

Google for "buck transformer". These seems to be purpose made for slightly lowering mains voltage.

Also Google for "AC servo drive faulting on over voltage" and you'll get a lot of results about regenerative braking causing a short period over voltage in drives. Seems to be a common problem on variable frequency drives.

I first read about that on the Gecko Drive website, but it was for stepper motors, and I even built some circuit boards for that. Never heard of any one else doing it though, and never heard anyone having stepper drives tripping on over voltage.
If you Google for something like "regenerative power dump circuit for AC servo motors" you might get some circuit ideas.

Keith
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adbuch
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Re: DMM Servo drive faults

Post by adbuch » Wed Apr 07, 2021 10:57 pm

Thor wrote:
Wed Apr 07, 2021 10:52 am
I've been chasing this issue for a couple years and still have not figured it out.

Candcnc Command CNC setup sending step and dir signals to DMM Dyn 4 servo drives and 750 watt servos.

I keep getting Y2 motor faulting out, usually either overvoltage or Lost Phase.

I have installed a Line reactor on the power feeding the drives as recommended by DMM to help with noise. I have replaced the encoder cable 2x now with brand new cable from DMM. Only difference between Y2 and all the other motors (Y1, X, Z) is that it has a shorter cables as its closest to the energy chain and control cabinet.

The overvoltage error, (when this appears it can be all drives) seems to be due to the fact that the drives kick out at 250vac and my incoming power is at 247vac (converted to 3 phase though a phase perfect digital converter). Seems like if my cnc turning center or mill is running at the same time, on a spindle ramp up or down the voltage spikes to 250-251 vac and trips the drive or all drives in the plasma. Power company said they dont care unless incoming is over 252vac with nothing running in shop.

I'm out of ideas on how to address either issue. Do I need to install a transformer just to power the servo drives? What would I even find to change from 247 to 240 vac? On the encoder issue I have tried running the drive end of the cable through a ferrite core a couple wraps, doesn't seem to help. Only other thing I can think of is to completely separate the torch cable to a new energy chain by itself. I have tried to keep it off to one side of the current chain and the encoders to the other side but doesnt help much either.

And I still need to wire up a fault signal from the drives to Command Cnc, so I don't have to babysit it all the time to watch for the gantry to go wonky.

Maybe its the DMM stuff, as I have them on my press brake retrofit as well, and the back gauge will go nuts occasionally there as well like hunting for position, but that uses analog command with encoder feedback to controller. Ughh, I need someone that knows this stuff to come spend a week and fix it all for me lol..

Any ideas appreciated, though I have tried more than listed here as well to no avail.
You very well may need to install a separate transformer to reduce the incoming ac voltage to an acceptable level. Some equipment manufacture , my Baileigh magnetic bending brake - for example, specify the min. and max. ac input voltage for their devices or equipment. In my particular case, my 240 vac power lines to the shop actually measure out to around 242 vac. I would check with the manufacturer of your equipment to see what the recommended input voltage range is.

The Baileigh instructions state:

"To achieve proper performance and prevent damage to the machine, the power supplied must be 220VAC +/-5% (209VAC to 231VAC). Failure to comply will damage the machine and void the warranty."

https://www.baileigh.com/magnetic-brake ... 4fEALw_wcB
Baileigh Magnetic Bending brake.jpg
I was able to accomplish this using a "buck-boost" transformer purchased on Amazon. This transformer is programmable by switching the wires to different terminals so that the desired voltage may be achieved.

The transformer I purchased about 3 years ago is the Acme Electric T181051 Buck-Boost Transformer, 1 Phase, 60 Hz, 0.50 kVA, 120 x 240V Input, 12/24V Output, Steel. It has worked great. The only thing I would recommend it to power down the buck-boost transformer when not in use. Otherwise it will be bucking (stepping down) your 240 ac line voltage, even with no load on it, and the transformer will get hot. So I plug mine in just before I power up my brake, and unplug it from the line source right after I power down the brake.

David

https://www.amazon.com/gp/product/B005G ... UTF8&psc=1
Acme buck-boost transformer.jpg

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Thor
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Re: DMM Servo drive faults

Post by Thor » Thu Apr 08, 2021 11:50 am

I emailed DMM tech support to see if they would recommend a transformer for me. Who knows it may fix the lost phase issue too.

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