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IndustryArena Forum > CNC Electronics > Dmm Technology > DYN4 Overcurrent, but only on initial startup
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  1. #1

    DYN4 Overcurrent, but only on initial startup

    Another over-current issue, but only when I initially energize the machine.

    DYN4 1kW 86M servos + DYN4-H01A2-00 drives
    Centroid Oak controller
    All power is 240V

    Logic power is on as soon as the machine is turned on. All the drives are fine at this point, green lights and no errors per the DMMDRV software. Once my control gets running it pulls in the contactors that connect the motor power to the drive and usually 2 of the drives will fault out with an over current error (not the same 2 though curiously, and sometimes all 3). After that e-stop won't clear the error. The only thing that clears it is cycling the breakers (logic and motor power).

    After cycling the breakers everything seems fine. I can induce faults and clear them with the e-stop and the servos seem to be running just fine. I can shut down the control software (Oak cnc software on PC) and bring it back up and it's still fine. Everything seems to work until I power off the machine.

    I have the drives wired per the attached (slightly modified) diagram from DMM. The only change to the original from DMM is that I have a line reactor on each drive after the breaker and before the contactor.

    Seems like it could be a timing issue with the drive enable signal but I'm not sure I really understand how that works with the Oak and Dyn4. I would think if it was noise, it would happen whenever I cycled the contactors and not just the initial power on.

    I think I've been staring at it for too long and would love to hear if someone else has any ideas, or things to try.

  2. #2

    Re: DYN4 Overcurrent, but only on initial startup

    I had the same problem. The fix is to power up the logic with the drive contactor.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3

    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by Jim Dawson View Post
    I had the same problem. The fix is to power up the logic with the drive contactor.
    That would be an easy enough fix for sure. I'll try that out this afternoon.

    Does it cause any issues with the machine loosing position if it's interrupted during a run? That was the only reason I had them separate previously. I've never run a CNC mill before though, so maybe it's a non-issue.

  4. #4

    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by Sam_Beckham View Post
    That would be an easy enough fix for sure. I'll try that out this afternoon.

    Does it cause any issues with the machine loosing position if it's interrupted during a run? That was the only reason I had them separate previously. I've never run a CNC mill before though, so maybe it's a non-issue.
    That is a problem. You will lose position on a power fail or other interruption. If your machine is equipped with home switches then it is not a problem to re-home. I have to re-home my lathe after a reset or on power up.
    Jim Dawson
    Sandy, Oregon, USA

  5. #5
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    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by Sam_Beckham View Post
    That would be an easy enough fix for sure. I'll try that out this afternoon.

    Does it cause any issues with the machine loosing position if it's interrupted during a run? That was the only reason I had them separate previously. I've never run a CNC mill before though, so maybe it's a non-issue.
    Try not to cycle any system On / Off to often, logic power should be on before the main supply this is, this is norm with all Servo Drives and should not be cut with the main contactor for the drive
    Mactec54

  6. #6
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    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by Jim Dawson View Post
    I had the same problem. The fix is to power up the logic with the drive contactor.
    Bad idea you have something else going on that is causing the problem you may need a snubber on the contactor or you are getting an over voltage at startup
    Mactec54

  7. #7

    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by mactec54 View Post
    Try not to cycle any system On / Off to often, logic power should be on before the main supply this is, this is norm with all Servo Drives and should not be cut with the main contactor for the drive
    In the case of the DMM drives I have to disagree with you here. If you power up the the DMM logic (L1,L2) before powering up the R,S,T terminals, the motor can briefly run away or go over current on power up. The proper way to wire it is per the DMM manual. I have done it both ways and found problems powering L1, L2 before powering R, S, T.

    The computer logic should be powered up before the drive.
    Jim Dawson
    Sandy, Oregon, USA

  8. #8

    Re: DYN4 Overcurrent, but only on initial startup

    This is a little frustrating. It seems like something that should be able to be handled through the servo enable signal. I'll see what DMM has to say. I know there were some fairly recent changes to firmware to accommodate the Oak, maybe mine aren't up to date.

    I have several schematics from DMM showing both power and logic being routed through the contactor. The ones they sent me (specifically for the Oak) have the logic power split off before the contactor so it's always on.

    I'm not going to be very happy if I have to loose my encoder every time the e-stop is depressed, or if I keep having to cycle the breakers with every startup.

  9. #9

    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by Sam_Beckham View Post
    This is a little frustrating. It seems like something that should be able to be handled through the servo enable signal. I'll see what DMM has to say. I know there were some fairly recent changes to firmware to accommodate the Oak, maybe mine aren't up to date.

    I have several schematics from DMM showing both power and logic being routed through the contactor. The ones they sent me (specifically for the Oak) have the logic power split off before the contactor so it's always on.

    I'm not going to be very happy if I have to loose my encoder every time the e-stop is depressed, or if I keep having to cycle the breakers with every startup.
    Please keep us updated on what DMM has to say. I had this problem on two machines.

    EDIT: There is a workaround, but it requires an external encoder.
    Jim Dawson
    Sandy, Oregon, USA

  10. #10

    Re: DYN4 Overcurrent, but only on initial startup

    Well DMM is saying it's likely the floating enable input causing the trouble (prior to the Oak coming online and asserting it's level). They said the Oak needs to be up and running before the drives get power. I really don't want to route the logic power through the e-stop contactor.

    I'm wondering if I could use a PLC output to control another contactor for logic power...

  11. #11

    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by Sam_Beckham View Post
    Well DMM is saying it's likely the floating enable input causing the trouble (prior to the Oak coming online and asserting it's level). They said the Oak needs to be up and running before the drives get power. I really don't want to route the logic power through the e-stop contactor.

    I'm wondering if I could use a PLC output to control another contactor for logic power...

    That's interesting. I had my controller powered up and stable and did use a PLC output to control the main drive power contactors. I was powering up the logic from the breaker and used the PLC to energize the drive main power. I did not try powering up the drive main power then powering the drive logic from a separate relay.

    A note on E stops, It should dump power to all outputs and motor contactors, but should not kill the controller or power to limit switches and other sensor devices.
    Jim Dawson
    Sandy, Oregon, USA

  12. #12
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    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by Jim Dawson View Post
    Please keep us updated on what DMM has to say. I had this problem on two machines.

    EDIT: There is a workaround, but it requires an external encoder.
    No you do not need an external Encoder, even if the drives are completely power off the Encoder will remember where it is at for up to 45min even without the optional battery powered backup

    And the servo motor can never run away no matter how it is wired up, they have a safety feature that will prevent any Encoder fault or motor run away
    Mactec54

  13. #13
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    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by Sam_Beckham View Post
    Well DMM is saying it's likely the floating enable input causing the trouble (prior to the Oak coming online and asserting it's level). They said the Oak needs to be up and running before the drives get power. I really don't want to route the logic power through the e-stop contactor.

    I'm wondering if I could use a PLC output to control another contactor for logic power...
    The Logic should never have anything to do with the Estop circuit, the control should always be the first thing that powers up then the power supplies and any other logic

    When you power up any machining center the computer is always first then all other low power and logic then main servo power

    I normally use a SSR to turn on all logic and power supplies then Reset turns on the main servo power, you don't need a PLC to do that
    Mactec54

  14. #14

    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by mactec54 View Post
    No you do not need an external Encoder, even if the drives are completely power off the Encoder will remember where it is at for up to 45min even without the optional battery powered backup
    Maybe with the absolute encoder option. I have no experience with that. This has not been my experience with the incremental encoder. The external encoders that I was referring to are linear encoders on the table, tied back to the controller. The only time that position is lost is on a computer power down.

    And the servo motor can never run away no matter how it is wired up, they have a safety feature that will prevent any Encoder fault or motor run away
    I had the runaway problem when I had the DMM logic powered (and stable) before energizing the DMM main power contactor. Many times, but not always, the motor would make up to about 50 uncontrolled revolutions at full speed before stabilizing. This problem ended when I wired the DMM logic to the main power contactor for that drive. The good news was that in that particular application, the motor could run freely without any danger of damaging the machine, unlike a machine tool with limited travel.
    Jim Dawson
    Sandy, Oregon, USA

  15. #15

    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by mactec54 View Post
    The Logic should never have anything to do with the Estop circuit, the control should always be the first thing that powers up then the power supplies and any other logic

    When you power up any machining center the computer is always first then all other low power and logic then main servo power

    I normally use a SSR to turn on all logic and power supplies then Reset turns on the main servo power, you don't need a PLC to do that
    I'm not sure I'm following. I am pretty much doing that right now but it doesn't work with these drives. I need to somehow stage the logic power to come on after the control has had a minute or so to come online.

    Using a spare output from the PLC to control another small contactor seems like it would be pretty easy to implement. It would basically just need to be TRUE whenever the PLC is running. I'm certainly open to other suggestions.

  16. #16

    Re: DYN4 Overcurrent, but only on initial startup

    Not sure if this will help you.

    I have four 1.8KW DMM units on my lathe. All wired with the DMM logic power wired to the contactors for the individual drives, per the normal DMM drawings.

    The startup sequence is:
    1) computer and controller power ON and stable
    2) control power ON, turns on hydraulic pump, some fans, 24V power, and 100VAC (yes, one hundred volt) power
    3) reset the controller
    4) pull out E-stop, allows the E-stop relays to be energized. Pressing the E-stop electrically disconnects power to the relay coils
    5) press servo power button. Controller energizes the E-stop relays, feeds power to the outputs. Pressing the E stop kills power to all outputs.
    5A) controller energizes the 4 DMM contactors with a 1 second delay between them so there is not a huge current inrush on the line.
    5B) controller energizes the DMM enable inputs. This is done with relays between the controller and the drives.
    6) press Home to home machine.

    Ready to make parts and the servos start up without problems.
    Jim Dawson
    Sandy, Oregon, USA

  17. #17

    Re: DYN4 Overcurrent, but only on initial startup

    Okay that’s similar to what I’ve been contemplating this afternoon. Are you using separate controller outputs for each of the DMM contactors or some other kind of delay? I think I’ve seen small din mount units that you can set on/off delays with. I was actually a little nervous about energizing all the drives at once, I’m guessing that’s a pretty good inrush current. Having those expensive line reactors probably helps there. I’m not sold on them really doing much else but DMM insists they need to be there.

    I’ve already got too much invested in this setup. Motor adapters and couplings, the cabinet was damn near built around them and probably most importantly, they are the only ac servos I’ve found which will physically fit on the x-axis of an old haas mill (with the exception of some really low powered ones). I will figure out some sort of workaround.

  18. #18

    Re: DYN4 Overcurrent, but only on initial startup

    Yes, I am using seperate outputs for the contactors. I have plenty of I/O to spare so I can get away with that.
    Jim Dawson
    Sandy, Oregon, USA

  19. #19
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    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by Sam_Beckham View Post
    I'm not sure I'm following. I am pretty much doing that right now but it doesn't work with these drives. I need to somehow stage the logic power to come on after the control has had a minute or so to come online.

    Using a spare output from the PLC to control another small contactor seems like it would be pretty easy to implement. It would basically just need to be TRUE whenever the PLC is running. I'm certainly open to other suggestions.
    Yes you could do it like that seeing you already have the PLC as part of your system, but at no time the machine is in run mode should the logic be able to disconnect only at power down of the machine
    Mactec54

  20. #20
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    Re: DYN4 Overcurrent, but only on initial startup

    Quote Originally Posted by Jim Dawson View Post
    Maybe with the absolute encoder option. I have no experience with that. This has not been my experience with the incremental encoder. The external encoders that I was referring to are linear encoders on the table, tied back to the controller. The only time that position is lost is on a computer power down.



    I had the runaway problem when I had the DMM logic powered (and stable) before energizing the DMM main power contactor. Many times, but not always, the motor would make up to about 50 uncontrolled revolutions at full speed before stabilizing. This problem ended when I wired the DMM logic to the main power contactor for that drive. The good news was that in that particular application, the motor could run freely without any danger of damaging the machine, unlike a machine tool with limited travel.
    With your jerry rigged incremental linear encoders system you use anything is likely to happen we where not talking about incremental encoders

    Absolute is the name of the game
    Mactec54

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