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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
    Join Date
    Mar 2004
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    136

    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
    Join Date
    Mar 2009
    Posts
    1982

    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
    Join Date
    Mar 2004
    Posts
    136

    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
    Join Date
    Mar 2009
    Posts
    1982

    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
    Join Date
    Mar 2004
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    136

    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
    Join Date
    Mar 2004
    Posts
    136

    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 ???Click image for larger version. 

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  7. #7
    Join Date
    Mar 2004
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    136

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

    hi everyone ,
    still need some help if anyone could help ..........PLEEEESe
    been doing some tests and still cant pin point it.
    Have measured the voltage (400vac) coming into the the OPUS 5000 power supply , both static and when the spindle starts. The voltage doesn't change a lot.

    The problem still happens with the spindle going over only 200 rpm ..controller /screen shuts down and the Alarm for under voltage come on the Opus 5000 power supply , but the multimeter still reads 400+ volts....so what i can tell there is no under voltage on the opus 5000 ......Anythoughts ??? anyone ?

  8. #8
    Join Date
    Mar 2009
    Posts
    1982

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

    AC voltage is not monitored. You need to measure the DC voltage on big capacitors.
    Could be problem with rectifier or something else. You need to locate the root of fault.

  9. #9
    Join Date
    Mar 2004
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    136

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

    Thanks for replying , But the alarm LED says

    "UNDER VOLTAGE OF AC INPUT"
    wouldn't that mean that AC is being monitored ?

  10. #10
    Join Date
    Mar 2009
    Posts
    1982

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

    There is no point to say: "the adjusted DC voltage drop on voltage input is detected". There is a chain of contacts, wires and components between the detection point and mains power supply input. You checked the AC input, it looks good. The circle of suspects become smaller. You need to follow forward to find out a bad contact or component.
    The "final" end is PSU, switching off when commanded because of the voltage drop. The point is to find what exactly the reason of the voltage drop is.
    If you will find the point with visible voltage drop when starting the spindle, you can easy decide what caused that. Could be damaged power diode, bad corroded contact or electrolytic capacitor ...

  11. #11
    Join Date
    Mar 2004
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    136

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

    ok , but im not saying anything , im just saying the facts,

    i will put simply.....here Mains 400 ac power source --------> to OPUS 5000 ( error LED ./...says UNDER VOLTAGE OF AC INPUT )

    I have not said anything about "the adjusted DC voltage drop on voltage input is detected"

  12. #12
    Join Date
    Mar 2009
    Posts
    1982

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

    The point is that the control has capability to detect the undervoltage ( and overvoltage ) of power supply. The evaluation is done far away from AC power terminals. The signal generated says "AC Voltage bla bla bla" because the most important reason to get the fault is the deviaton of AC voltage on mains terminals. You tested the AC voltage and it is clear, that AC on the power terminals is correct. Right?
    Since the fault message is still there, it's necessary to find out what the reason is. Right?
    Is there point to say that voltage dropped on the detection point? No, of course. You need to find where it drops when the spindle starts. Next point is on the PSU capacitors after rectifier.

  13. #13
    Join Date
    Mar 2004
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    136

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

    ok, but im not an electronics engineer so im only reporting my findings.
    thanks anyway
    cheers

  14. #14
    Join Date
    Mar 2009
    Posts
    1982

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

    Your start of diagnostics is quite effective. Since 400VAC is correct, next step is taking the same measurement on the next point. You will find loose contact or burnt component going that way most likely.

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