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Thread: Robust VFD Question

  1. #16
    If your drive is kicking out, you should be getting an error code. If you have the error code, maybe Robust could provide you more insight on any changes needed. If you're not getting an error code, you probably don't have a VFD problem, but may have some other intermittent electrical problem, like a funky switch. That may also explain why your problem seems to be intermittent.
    "Only a rich man can afford cheap tools, as he needs to buy them again and again"

  2. #17
    Join Date
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    Quote Originally Posted by Jason Edwards View Post
    If your drive is kicking out, you should be getting an error code. If you have the error code, maybe Robust could provide you more insight on any changes needed. If you're not getting an error code, you probably don't have a VFD problem, but may have some other intermittent electrical problem, like a funky switch. That may also explain why your problem seems to be intermittent.
    Jason, you may be correct on this. In addition to a funky switch, some motors have a thermal cutout switch buried in the windings. Some are self resetting.

    I look forward to seeing what Clay discovers when he has time to trouble shoot this some more.

  3. #18
    Quote Originally Posted by Clay Fails View Post
    Hello all,
    I am turning with a Robust American Beauty with the 3 HP motor. It is fitted with a Toshiba VF-S15 VFD.

    After turning hundreds of bowls in the past 4 years, recently the drive has begun cutting out under load. I don't mean belt slippage, I mean complete electrical cutout.

    Has anyone else had this issue, and if so, what parameter on the VFD did you adjust? I'm guessing it has to do with amp draw, but have not yet dived into the parameter list.

    Please don't suggest I contact Robust, because I did and the response was maybe I should learn how to turn. I would have given that some thought had I not already successfully turned a cajillion bowls and this is a new phenomenon.

    thanks in advance,

    Clay
    Just a thought, after reading all the thread comments and rereading the original post it appears to me that one thing that could contribute to the issue described is a loose connection. When turning hard woods there may be a high frequency vibration that doesn't occur with green wood. Because this issue seems to have surfaced after several years of use and appears to be intermittent that leads me to think loose connection not fall out loose but just enough to cause the smarts in the VFD to recognize. In industry we used to do a PLC IO board tighten /check every couple of years, amazing how many points were found slightly loose.

  4. #19
    Have not seen anyone ask this....so - Are you using a dedicated or shared electrical circuit? If shared...what else is on that circuit...could that create enough of a temporary load to create the non-errorcode stalls?
    Hope that helps...
    T

  5. #20
    Join Date
    Jan 2011
    Location
    Wilmette, IL
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    Second the switch suggestion. I can and do stall or at least slow my AB when running at slower speeds and taking a big bite. That is a mechanical stall, I have never tripped the drive. However, from time to time, both the start/direction switch and the stop button get gunked up. This results in a refusal to start if it is the switch or a sudden stop if the issue is the stop button. Blowing out the switch fixes the issue. The root cause is dripping wet, green wood leaving the lathe, the control box, and me pretty wet.

    Also second Brent English as a stand up, genuinely decent guy.

  6. #21
    Join Date
    Mar 2013
    Location
    Eastern NC
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    Does your pendant stop switch have a boot (cover) or is it just the a bare push button? My AB had intermittent issues of not starting and then it wouldn't start. Brent correctly/quickly diagnosed it as the switch and talked me through the trouble shooting (had to remove the spindle lock switch and verify it was working properly). Brent sent a replacement switch since I was under warranty. Obviously not the same as your problem. but you might consider opening the pendant and seeing if it is 'dusty' in there. And maybe blow out the head stock?

  7. #22
    I know nothing of your VFD circuitry....but the behavior you describe is like that of a bi-metal thermal protector....which I do know a bit about. They are designed to cut out when high currents are sustained. They have a little heater that heats up the bi-metal disc....and then the disc snaps. After cooling down, it snaps back into place. If you apply high current again, it is already heated up and will snap quicker.
    Either way....your circuitry is experiencing a high current condition.
    Measuring the current is the best start
    ~john
    "There's nothing wrong with Quiet" ` Jeremiah Johnson

  8. #23
    Join Date
    Dec 2012
    Location
    North East, PA
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    242
    Well, again I thank you all for the thoughtful input.
    After several days of turning with no issues at all, again today the motor started tripping out on a fairly hard maple burl. When this happens the Toshiba VFD LED displays 0.0, which I believe is the default status when the motor is not running. From reading the Toshiba literature it looks to me like if in fact the drive trips out, the error code would automatically display (i.e. i would not have to scroll through the menu to find the error code).

    so if all that is true, maybe the drive is not in fact tripping out at all. Could this be a motor internal thermal protection circuit that is cutting out? John Hart's comments have me wondering because once this issue appears, it tends to continue indefinitely until I walk away and come back later. That might indicate some thermal issue of some kind.

    So any ideas on how I should proceed? If the Toshiba is tripping the error codes must be saved somewhere but I haven't yet figured out how to retrieve them.

  9. #24
    Join Date
    Dec 2012
    Location
    North East, PA
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    242
    Quote Originally Posted by Bert Delisle View Post
    Just a thought, after reading all the thread comments and rereading the original post it appears to me that one thing that could contribute to the issue described is a loose connection. When turning hard woods there may be a high frequency vibration that doesn't occur with green wood. Because this issue seems to have surfaced after several years of use and appears to be intermittent that leads me to think loose connection not fall out loose but just enough to cause the smarts in the VFD to recognize. In industry we used to do a PLC IO board tighten /check every couple of years, amazing how many points were found slightly loose.
    Bert, thanks for the idea. Do you know which connections I would check for looseness? Are we talking about the leads at the motor, or at the VFD, the on/off switch or all of the above?

  10. #25
    Join Date
    Dec 2012
    Location
    North East, PA
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    242
    Quote Originally Posted by Tim Tucker View Post
    Have not seen anyone ask this....so - Are you using a dedicated or shared electrical circuit? If shared...what else is on that circuit...could that create enough of a temporary load to create the non-errorcode stalls?
    Hope that helps...
    T
    Tim, it's a dedicated circuit. The only other 230/240V machine that runs while I'm turning is my dust collector, but that's on a separate circuit.

  11. #26
    Join Date
    Dec 2012
    Location
    North East, PA
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    242
    Quote Originally Posted by Eugene Dixon View Post
    Does your pendant stop switch have a boot (cover) or is it just the a bare push button? My AB had intermittent issues of not starting and then it wouldn't start. Brent correctly/quickly diagnosed it as the switch and talked me through the trouble shooting (had to remove the spindle lock switch and verify it was working properly). Brent sent a replacement switch since I was under warranty. Obviously not the same as your problem. but you might consider opening the pendant and seeing if it is 'dusty' in there. And maybe blow out the head stock?
    Eugene, thanks for that thought. A couple years ago Brent at Robust sent me the new pendant assembly because the original one was sticking as you note. Since then the switch has performed flawlessly. So I don't think that's my problem but at this point I"m not sure of anything.

  12. #27
    Check all the high voltage connections that you can. Wire and connections heat up and cool down alot. This can cause expansion and contraction of mechanical connections causing them to loosen up. My other hobby is home brewing. I have an electric system that uses 220v elements. After 4 to 6 brew sessions i go in and tighten up all the screw down connections and check the spade connections. You would be surprised how much the screw down connections loosen up and there is no vibrations in my control panel.

  13. #28
    Clay you insinuated that the inverter is holding back the motor from reaching it's full potential. Do you have any relevant data to substantiate that statement? I'm an electrical engineer with quite a bit of experience in various types of systems involving motor control. I've had a Robust AB for eight years so my model is the one that preceded yours, however, as far as I know the inverter is the same, but the motor is a different frame size to work with the new style headstock casting. I'll clear up one thing right away ... the inverter isn't limiting the performance of the motor. And, I would say that the inverter isn't failing because as a rule digital electronics either work right or they don't work at all. I'll offer a couple thoughts ... some might have already been discussed.

    • There is always a possibility of the motor failing. The probability is very low, but not zero. Mechanical devices eventually fail, but the Leeson and Baldor motors used by Robust are high quality. The most likely conditions for early failure are extended periods of heavy load at any speed, but especially minimum speed operation under heavy load which leads to the motor overheating.
    • The inverter might be cutting out when it's temperature gets too hot. There are numerous possible reasons:
      • Heavy load operation for extended periods of time
      • High ambient temperature
      • Dust and shavings blocking the airflow around the inverter
      • Inverter cooling fan not working or periodically stopping ... you should be able to hear the fan running
      • Try blowing all the dust out of the inverter as well as its electrical enclosure

    • The motor has a thermal cutout switch so it might not have anything at all to do with the inverter ... it might simply be the motor getting too hot
    • The display on the inverter is the frequency so 0.0 would be seen when the lathe is stopped or if the speed control pot is turned all the way down. Intermittently going to zero could be the result of an intermittent FWD/REV/STOP input or an intermittent open circuit from the speed control pot.


    When I got my Robust I also got a full users manual on CD for my Toshiba inverter. I have spent quite a bit of time perusing it. I would strongly recommend that you don't go diddling with any of the settings unless you thoroughly know what you are doing. Changing one thing often has a ripple effect on other parameters. However, it won't hurt to read through some sections of the manual to at least have some familiarity with it. There are some settings that can be safely changed such as ramp up and down times.

    As far as lessons are concerned, I don't know anybody who isn't a better turner as a result of taking lessons. I've been turning for nearly sixteen years and still jump on an opportunity to take lessons ... this year it was with Michael Hosaluk.
    Last edited by Bill Boehme; 09-12-2019 at 10:44 PM.
    Bill

  14. #29
    Clay is your lathe past the 7 year warrenty or does the warrenty not cover electrial issues?

  15. #30
    I'm going to reiterate my note above, if you're not getting an error code, you probably have a switch problem. I suggest you call Robust and see if they can help you trouble shoot it.
    "Only a rich man can afford cheap tools, as he needs to buy them again and again"

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