Losing steps/position, again

[dazp1976]

That's WRONG information your giving out, the drives don't regulate the voltage they regulate the current. 70Vac which is 98Vdc would destroy those little motors in no time at all. It would also make them run like a bag of shite.

You cannot stick any voltage you like into a stepper, there is a limit where it starts to have very negative affects. Namely iron losses and motor heating which kills them.

Those Large voltage Ac drives are only really any good for larger steppers Like Nema 34 or very high inductance NEMA 23's. Your typical 3-4Nm 4.2a Nema 23 with 3-4mh inductance doesn't like to be run much more than 80vdc and at that, you are pushing them past there design threshold so are shortening there life.

For the NEMA 23 motors, which this machine will have fitted he'll only need drives with a max rating of 70Vdc and would run them around 55-60Vdc. Or 50Vac drives running at 40-45Vac.

Steppers are generally all rated 2-3Vdc yes?. So if said nema 17 / 23 or 34 (2-3Vdc) were put on the same driver why would I only blow the 17? (unless I didn't change the current output).

Also inductance. There are Nema 34's out there that are abysmal running on 60V supplies and ideally need at least 120Vdc to work reliably.

Also there are now drivers on the market with direct 240Vac input connections so no need for psu's anyway. These are aimed at nema17-23 size. Why would these not burn them up either?

I and many others use 60Vdc at least using larger 34 size drivers to run nema17 & 23 size motors. Even that goes against the grain and it's worked for years.

[AndyUK]

Steppers are generally all rated 2-3Vdc yes?.

My understanding is that if you give a coil on the stepper the rated voltage (2-3V) it will draw the rated current.

If you give a stepper a higher voltage, the current will also increase and the thing will burn up.

But we're not doing that - we're using stepper drivers. These give the motor the full voltage in "punches" to limit the average current to a set value. Therefore its entirely reasonable that the voltage supplied to the driver is important for the reasons Jazz sets out.

Blanket recommendations are dangerous either way - you need to consider all the factors like the steppers inductance and current limits to determine what will blow and what won't. NEMA 17 or 23 is just a mounting size, and has no real effect on this.

[JAZZCNC]

Steppers are generally all rated 2-3Vdc yes?. So if said nema 17 / 23 or 34 (2-3Vdc) were put on the same driver why would I only blow the 17? (unless I didn't change the current output).

I didn't say it would blow it up, I said it would destroy them and this is true. They couldn't handle the heat and that would kill them eventually depending on voltage.

Also inductance. There are Nema 34's out there that are abysmal running on 60V supplies and ideally need at least 120Vdc to work reliably.

Also there are now drivers on the market with direct 240Vac input connections so no need for psu's anyway. These are aimed at nema17-23 size. Why would these not burn them up either?

You'll find that many of the drives that use 240Vac won't run small motors for the same reason I mentioned before, most don't even limit current below 5a. The drives you speak of which use AC voltage and can run Nema 17/23 use Low AC voltage which you transform down from 230Vac and that gets rectified to DC in the drive.

I fit 230 Vac drives all the time and I can tell you that if I fitted those little motors or nema 17 motors to the drives they would be fried within hours. Even with small (4nm) Nema 34 motors you have to be very careful and make sure you limit current correctly because current it proportional to Voltage and you cannot limit the voltage so they get hot.
This is physics it's not me making shit up and just because you haven't experienced it doesn't mean your correct it what your saying. Unless you know it to be true then I suggest you STFU because it's hazardous to components life and even dangerous in some circumstances.

I and many others use 60Vdc at least using larger 34 size drivers to run nema17 & 23 size motors. Even that goes against the grain and it's worked for years.

No it's doesn't go against the grain and it's perfectly acceptable because the voltage is much lower and the motors can handle it. Again physics comes into play and there is an ideal voltage where motors run with-in safe tolerances, most people running more than 60vdc with NEMA 17/23 motors are running past the motor's ideal voltage but only just so it's not a problem. Think of it like overclocking a PC, it works but will shorten the PC's life unless it's cooled better, same shit here.! . . . Running higher than ideal voltages your actually shortening the motors life but who cares because it's going to take years if only 10-20v over but double the rated voltage or more and it won't take long. (unless cooled massively)