how to drive THIS stepper motor.....

I have been driving this step motor:
www.alltronics.com/mas_assets/acrobat/28M046.pdf ,


...connected bipolar parallel, for some time on my diy router table with good luck. However, the motor has never-ever-ever, I do mean ever :tired:gotten even the slightest bit warmer than ambient. So I have started to assume I could drive it much harder?? I am driving it using a Gecko G203 and have it set with the current set resistor at about 6 amps, based on the datasheet recommendations of 5.5 amps per phase(fudged upwards a smidge since it does not get warm).

But it finally dawned on me that perhaps I have misunderstood the datasheet, or the basic parallel vs. series driving requirements in general, and that I could drive this at 11 amps(5.5 X 2) when wired parallel. Problem is, a google search for "high current step motor drivers" reveals nothing on my end that beats the 7 amp max of the G203.

So my questions are:
1) Am I correct in thinking that I can safely operate this motor at 11 amps when connected bipolar parallel?
2)If so, would I be better off finding some microstepping drive that can operate at 11 amps(does it exist), or reconnecting this motor as bipolar series and set the appropriate resistor for 5.5 amps?

The main complaint with the current setup is the lack of acceleration on the axis. I am driving a relatively heavy gantry(about 150 pounds) using this motor via a single high lead ballscrew, and although my feedrates and rapids are very satisfactory, I never get to these speeds on this axis due to the low acceleration and relatively small table size. And when using constant velocity settings on quick roughing operations, I get very exaggerated results.

thanks:cheers:

I wouldn't worry about your motor not getting hot. But what are you using for a power supply? It's voltage, not amperage, that determines how fast your motors can accelerate. How many volts are you giving it? Those drives can take up to 80v, which should make that motor perform pretty well.

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Originally Posted by awerby

It's voltage, not amperage, that determines how fast your motors can accelerate.

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I am using a converted 48 volt switching power supply from a server.

So if I used a current set resistor to set the current 1/10 of the original 6 amps, to .6 amps, I would still be able to get the exact same acceleration performance since the voltage is the same? Because on my machine, I am certain that at lower current settings, I begin to miss steps at lower acceleration settings and feedrates.

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Originally Posted by billcat

I am using a converted 48 volt switching power supply from a server.

So if I used a current set resistor to set the current 1/10 of the original 6 amps, to .6 amps, I would still be able to get the exact same acceleration performance since the voltage is the same? Because on my machine, I am certain that at lower current settings, I begin to miss steps at lower acceleration settings and feedrates.

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STP-DRV-80100 | Stepper Drive: microstepping, max 10A per phase, 2-phase bipolar
Copley Controls - Stepnet - Stepper Drive - CANopen - CAN bus - STP-075-10

both will output more than 10amps - you don't want to do this though.

Whats the problem you're trying to solve?

An 8 wire stepper can run 1.4 times the current running in parallel vs unipolar.
This means you could go to 7.7 amps with these steppers.
If your drivers are limited to 7 amps I would change the drive to that level.
This will give you 16% more power.
Since steppers are large inductors the higher the voltage the quicker the coil can get up to the maximum amps required.
This becomes important at high speeds since the coil may not have time to get to required current before the current it has to switch directions for the next step.
You still need the current level.
Have you checked the voltage of the power supply to see that it keeps it voltage level under load. If not it may not be supplying the required current.

George

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Originally Posted by UA_Iron

Whats the problem you're trying to solve?

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Quote:

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Originally Posted by billcat

The main complaint with the current setup is the lack of acceleration on the axis.......

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Quote:

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Originally Posted by george4657

An 8 wire stepper can run 1.4 times the current running in parallel vs unipolar........
Have you checked the voltage of the power supply to see that it keeps it voltage level under load?

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So might I assume that the one current rating given for my motor in the linked .pdf of the OP would be the rating if the motor is used unipolar?

I have tested voltage on my PS while under heavier load than I expect from the step motors using a large BLDC motor spinning a propeller with a live mode data logging device connected to observe the current, voltage, and power. I also had a Fluke DMM connected and there was no sag whatsoever.

I am still curious if I would be better to rewire this motor bipolar series and use the same Gecko driver set at 3.85 amps......? 1.4(parallel) x 5.5(unipolar) / 2 (series)

Your voltage is killing your power output according to lin engineering.

Check out the graphs, 48V vs 80V.

interesting...didn't realize just how substantial the higher voltage affects torque @ given rpm.

guess I will have to get a bigger power supply or just live with the low acceleration. I will set the G203 for its max 7 amps first, maybe that will help enough to forget about upgrading the PS for awhile;
been pretty satisfied with the machine as is.

thanks for the info folks!