New motor and vfd?

  1. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
    Ive blown the warco lathe motor, and wanted a new one anyway with more low speed torque. It is instantly tripping the 30A circuit breaker, nothing else turned on. Im suprised the lathe control fuse and plug fuse is fine.

    Please recommend a motor/vfd, if that is the best type?

    Current motor 110mm dia x 250mm long rated 1kw, could probably go to 140mm before stuff gets in the way.

    Thanks
     
  2. eLuSiVeMiTe

    eLuSiVeMiTe Forum Supporter

    Messages:
    8,634
    Location:
    Bedfordshire England
    Assuming it was a DC motor originally.
    Speed?

    Could you mount separately behind the lathe and negate the original mounts to allow a larger size for an ac 3p motor
     
  3. m_c Member

    Messages:
    31
    Location:
    East Lothian
    DC motors are usually far more powerful for any given physical size compared with standard AC motors.

    A key point to understand, is electric motors are constant torque. They only produce their rated power at rated speed, so half speed, and you half power. There are ways to boost torque, but you risk cooking the motor.
    If you're doing a lot of work that requires lower speeds, it may be worth gearing any new motor to reduce maximum speed and increase torque.

    For possible replacements, check inverterdrive.com

    If adding an inverter, it is possible to overspeed motors.
    As standard on 50Hz, a 2 pole motor will run at just under 3000RPM, and a 4 pole at just under 1500RPM. With an inverter and suitable inverter rated motor, you can run the motors far faster, so you can do things like run a 4pole motor up to 3000RPM. The caveat is once you pass the rated speed, the torque starts to decrease as the motor is then running at constant power not constant torque, but for lathe use, that's not likely going to be an issue. But the big benefit is you'll get twice the torque upto 1500RPM compared to using a 2 pole motor, although the 2 pole motor can potentially be a smaller frame size.
     
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  4. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
    The pulley reduction was about 4.6:1 (25-116mm minor dia of pulleys). Max motor speed around 5k. Im quite sure heat killed it - the body was hot but I cant see any damage to rotor.

    [​IMG]
     
  5. m_c Member

    Messages:
    31
    Location:
    East Lothian
    You may struggle to fit an AC motor in there.
    Page 10 on this manual lists all the motor dimensions - https://inverterdrive.com/file/TEC-AC-Motor-Technical-Catalogue-IE1-IE2-v3
    (if the direct link doesn't work, scroll down this page to the bottom of the details section for the link - https://inverterdrive.com/group/Motors-AC/ac-Motor-750W-750-Watts-2-Pole-B34-Foot-Face-TEC/)

    It's most likely just the motor controller that's died. The FETs/SCRs start to short out under load, which causes the problem you describe, and the nature of the transients/currents involves will often trip a MCB before blowing the fuse. If you wanted to replace it with a bit more robust drive, search for a KBIC 240, however you may find the motor is faulty as well.

    The other option would be an AC servo motor (similar power/volume ratio as a DC motor) and drive, but that would come with increased cost and/or complexity.
     
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  6. Pete.

    Pete. Member

    Messages:
    8,272
    Location:
    Kent, UK
    It's the DC drive that normally pops. It if's blowing the 30A breaker but not the fuses then it's probably an earth fault tripping it. Try un-plugging the motor from the drive and see if it still trips.
     
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  7. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
    Reassembled motor and connected up to a 24v lipo pack and cordless speed control switch, runs about 500rpm. The control board is a KBlC 240, its dead, no damage visible but resistance on the fets is 0.2r.

    I think a 3ph motor will fit and can go upto 250mm diameter, so should have better torque, problem will be increased length hitting the chip guard. Difficult to match up models to dimensions.
     
  8. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
  9. m_c Member

    Messages:
    31
    Location:
    East Lothian
    Does that still leave enough clearance so the cooling fan isn't restricted?

    Going up a pole count, will mean you can use a larger pulley, but if you'll be doing a lot of running at low speed, you may have to look at forced cooling to stop the motor from overheating.
     
  10. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
    Nice thing about ac motors they have better cooling and are sealed (TEFC) so should be no problem to have it poke into the chip tray area. The chip tray is not sealed and I did some have problems with swarf getting the dc motor.
     
  11. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
    Ill probably order from inverterdrive.com. They reccomend buying a TEC brand inverter with the motor to get double the warranty on both. The 1.5kw 6pole motor is very close to the inverter current limit 6.5a vs 7a. The next one up is too expensive.
    https://inverterdrive.com/group/AC-Inverter-Drives-230V/TEC-3-120070-1F12/
    The cheap ones are all IP20, unsure if dust,swarf and condesation will be an issue?

    How important is the emc C1/C2/C3 rating if using on a residential 13a plug?

    https://inverterdrive.com/group/AC-Inverter-Drives-230V/Siemens-V20-6SL3210-5BB22-2AV0/
     
  12. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
  13. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
    29mm spindle diameter, 4mm key. Not a standard size for taper lock pulley :dontknow:
     
  14. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
    [​IMG]

    Its bigger in person, hope it bloody fits :D
     
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  15. m_c Member

    Messages:
    31
    Location:
    East Lothian
    Where did you get those dimensions?
    Sounds more like 1 1/8" (28.575mm) shaft with a 5/32" (3.968mm) keyway.
     
  16. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
    [​IMG]
     
  17. m_c Member

    Messages:
    31
    Location:
    East Lothian
    Ah. That makes more sense.

    I'd go for the imperial taperlock, and if need be, bore it out slightly. I wouldn't personally worry about having a key, as this application won't be pushing the torque limits of a taper lock fit very much.
     
  18. Kram

    Kram Member

    Messages:
    544
    Location:
    Sussex
    She fits.

    [​IMG]

    Without the chipguard :ashamed:

    [​IMG]

    I may be guilty of buying the most powerful lump that doesnt actually fit :D It will be mounted a couple inches lower (with a big hole in the chip tray to allow it). Edit - yes it will have a full cover to prevent any chips getting at it when done.
     
  19. Seadog

    Seadog Forum Supporter

    Messages:
    4,513
    Location:
    NE London - UK
    A bit over the top, I think. You'll need to take care of flying swarf and cutting oil getting sucked into the fan end. Or buy a smaller motor :scared:
     
  20. Pete.

    Pete. Member

    Messages:
    8,272
    Location:
    Kent, UK
    You'll want to make a sheet cover to keep swarf out of that. I had to do it on one lathe.
     
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