Acorn analog 10v & AC Servo drive RPM questions


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Thread: Acorn analog 10v & AC Servo drive RPM questions

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    Default Acorn analog 10v & AC Servo drive RPM questions

    I have an Acorn with H3N-TD servo drive I'm setting up to drive a spindle on my mill. I am currently running a 110ST 05030 and I also have a 130ST 05020 but I'm leaning towards the servo rated for the higher RPM since I plan to run it at the limit of my drives capability of 3,300 RPM. I'm not sure if the 130ST 05020 isn't exactly the same as a 130ST 05030 just rated for 1KW 2K RPM vs 1.5KW 3K RPM. I have run the 130ST 05020 at 3,000 and it seemed just fine but I assume pulled the full 1.5KW/6A.

    Anyways back to my question. I'm setting up Acorns RPM and have run the analog test with my multimeter to ensure my Acorn is within the rated 10% on analog output(it's well within so no issue there). So far I have tested a few analog wire setups and settled on a 23AWG CAT6 cable that is twisted and shielded but not individually shielded in pairs like a CAT8 cable.I found that I needed the shielding grounded to the DB26 header on my servo drive as well as grounding the other end to the Acorns DB25 connection because without it my drive would run up to 10-20 RPM randomly. My drive also has a feature called zero offset that "automatically detects the zero bias" which I have programmed while at 0 RPM and this too helps although it skews my actual RPM by 100-150RPM at a minimum. Even with the zero offset calibrated I still had some very minor hunting so I adjusted the minimal analog RPM from 3 to 50 and this finally fixed the motor to zero RPM while Acorn is set to 0 so I adjusted Acorns minimal RPM accordingly. Lastly I adjusted "analog speed command gain" to 330 (I assume 10v x 330=3300) and I get my peak RPM of 3300 and more closely match the set RPM throughout the range.

    After doing all of this I find my higher RPM settings more closely match Acorns set value but the lower RPM values are off by a larger amount then the higher RPMS which are within a few RPM at/over 3,000. Now my question is, am I doing this correctly? Is there a suggested route to follow? I would love to ditch the zero bias and get my RPM to more closely match my real RPM but I'm kind of concerned of randomly movement down low plus my servo drive has an encoder pass through so I'm considering rigid tapping at some point in the future.

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    Default Re: Acorn analog 10v & AC Servo drive RPM questions

    Did a little more adjusting and with the analog "voltage to RPM" gain @ 326 my RPM is off by 50 at 100 RPM, 40 AT 500 RPM, 20 at 2,000 RPM and so on.



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    Default Re: Acorn analog 10v & AC Servo drive RPM questions

    Disabled the zero RPM offset and then raised "minimum speed limit for analog" until the motor quit turning and 240RPM is low as I can go at 0v and not see any rotation or feel "jittering". Problem is then the speed is off by 130+ RPM with 330 speed to analog input gain and lowering the gain just screws up the scaling of voltage to RPM. I think my best bet is to try and run as low of a zero offset as possible and adjust the minimum RPM accordingly unless someone can tell me another way of doing this.



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    Default Re: Acorn analog 10v & AC Servo drive RPM questions

    Managed to find a happy medium. Set zero offset to 90, minimum analog RPM to 75 and analog to RPM gain @ 320. This results in the speed being off by about 15 RPM starting at 75 and climbs in a mostly linear fashion to be off by 2 RPM at 3,300. Hopefully this will help someone in future with a similar drive and I would love any tips on improving this further.



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Acorn analog 10v &  AC Servo drive RPM questions

Acorn analog 10v &  AC Servo drive RPM questions

Acorn analog 10v &  AC Servo drive RPM questions