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IndustryArena Forum > MetalWorking Machines > Okuma > Okuma LB10 spindle starts then system shuts down.... low power problem ???
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  1. #1
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    Mar 2004
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    Okuma LB10 spindle starts then system shuts down.... low power problem ???

    Hello Everyone,
    if anyone had some thoughts on this would appreciate some help and or any advice in trouble shooting.

    Bought an old Lb 10 Okuma Lathe which i believe was working ok when i bought it.
    having used it a few times im now having trouble with the
    spindle powering up. I can use Midi and select spindle speed of only maximum of 100rpm and then increasing slowly to 200rpm but then the controller / monitor shuts down. There is still power to the machine and can hear the hydraulic pump after it shuts down. When the system shuts down i can hear a contactor make a noise (open or close) .....presuming insufficent power then contactor opening ....maybe

    Im using a rotary three phase converter and its good for about 15amps at 415 volts.
    I understand that the Okuma i have has a 15 horsepower spindle motor and is probably a little more needed from the Rotary phase converter but i figured if i take it easy then would be ok.

    When i first got it i could start the spindle no problem to at least 1500 rpm then over a few time it started shutting the controller off. I then had to reduce spindle RPM until now where i can bearly turn the spindle on. So i think i have damaged something because of low power ? but what ?
    Also when this happens i get a AC LED on in the back electrics cabinet on the OPUS 5000T indicating
    "UNDER VOLTAGE ALARM OF AC INPUT "
    I tried a 30 KVA generator and it didnt do any better. Same result.

    Anyone with some ideas or help would be great ....

    Thanks in advanced

  2. #2
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    Mar 2009
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    Re: Okuma LB10 spindle starts then system shuts down.... low power problem ???

    Rectifier can help.
    Check the DC voltage on big capacitors. It's not likely that something is damaged because of low power. More likely, there were spikes powerful enough to damage a capacitor or two.

  3. #3
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    Mar 2004
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    65

    Re: Okuma LB10 spindle starts then system shuts down.... low power problem ???

    Thanks for your reply . Much appreciated.
    When i open the back electrics cabinet there are hundreds of Caps
    Any chance of a walk through in fault finding, what caps to test ?

    Everything else works as it should , its just the spindle hasn't enough power.

  4. #4
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    Mar 2009
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    1446

    Re: Okuma LB10 spindle starts then system shuts down.... low power problem ???

    Big high voltage DC capacitors must be located somewhere at main power supply. They are also installed in the drive unit itself.
    Check the spindle drive unit power transistors ( MGBT modules ) - maybe the reason of fault is there.
    Have you possibility to take measurement of momentary current flow?

  5. #5
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    Join Date
    Mar 2004
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    65

    Re: Okuma LB10 spindle starts then system shuts down.... low power problem ???

    Unfortunately thats well above my skill and knowledge level ....will need to get some one in whos knows lots more then i do

  6. #6
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    Join Date
    Mar 2004
    Posts
    65

    Re: Okuma LB10 spindle starts then system shuts down.... low power problem ???

    Algirdas , tried to PM you a photo of the fault LED im getting on the okuma power supply .....but couldnt so will post here.
    Maybe someone else would like to comment ???Attachment 461790

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