Okuma LB15 201 Drive Alarm

[RLMTS]

Hello All,
Here's hoping that you Okuma wizards can help us.

(LB15 OSP5000)

On start-up the machine often boots to the main screen but with Alarm 201.
The Okuma manual describes this as a possible BDU fault or a Servo PSU fault.

Also, immediately at mains power-on, the Z-axis drive shows red LV LED. (is this normal?)
For this' the manual says replace either BDU or Servo PSU.

Eventually, it does becomes possible to reset the machine, but this can take hours.

This is how I have progressed so far...
------------------------------------------------------------------------------------------------------------------
Machine giving Alarm “201-4 Alarm A Servo Amp Z Axis” Error
(Sometimes we get 201-3 X axis error instead?)

Tried to restart numerous times, same error.

Proceeded to check all voltages:
415v 3ph = 416v
200v 3ph from transformer = 200v
Transformer tapping was set to 415 = OK
100vac = 102vac
110vac = 112vac
LV Power Supply...
5vdc = 5vdc
12vdc = 12vdc
24vdc = 24vdc
ISO 24vdc = 24vdc

All these values appear to be OK

Red LED on BDU Servo PCB indicating “LV Error”
Red LED on Servo P/supply indicating “LV Error” (This not always on)

LV refers to DC Drive power was below 200vdc.
Located DC Bus supply (HV and LV) tested and was at 288vdc
(Checked adjacent machine (which was running) this also at 288vdc) (but this other machine also gives same 201 error but much less frequently).

Also occasional Red LED “IOCS” on Servo Amp PCB (BDU)
This refers to “More than 120% transistor rated current flowed through transistor bridge” (Power transistors feeding motor)

Disconnected Z axis motor terminals, powered up and fault had cleared.
Did this restart twice and was ok both times. Reconnected motor, powered up, fault re-occurred.
Disconnected motor again, but this time the 202 fault reappeared.???

Noticed that red LED “LV” on servo PCB comes on as soon as isolator is turned on, not sure if this is normal?
This also happened when motor was not connected but extinguished when CNC had fully booted up.

The Okuma maintenance manual has action for these faults...
If BDU LV LED then “Replace BDU Unit, Replace Servo DC P/Supply”
If IOCS LED then “Replace BDU Unit”

If the Okuma manual is correct, I believe I am unable to progress much further without parts.
Even so, could the machine may be incorrectly reporting that these parts require exchanging?
Without spares to swap out we cannot be absolutely sure.

The IOCS fault was strange, indicating high current in the motor drive transistors? (This happened when motor was still connected) I wonder if there is an issue with the servo drive power section (behind PCB)

The motor was checked (multimeter only) and showed balanced phases at approx.1 ohm, and over 20 Megohm to earth. (Did not have ‘Megger’ to test earth)

Is it possible that the drive DC bus (LV-HV) at 288Vdc is too low?

Any help/advice much appreciated.

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[old timer okuma]

As long a the DC bus stays above 240 DC from VH to VL you should be fine. It needs to be 300 DC (assuming 220 incoming), but if you incoming is at least 196 AC you should be fine. The ohm reading to ground sounds low. I would suggest borrowing a megger and double checking again. If less than 10 meg the motor is shorted, less then 100 meg the motor is damage the drive.

[RLMTS]

Thanks Old Timer. We will get motor checked with megger. But error sometimes occurs on the other axis?
And occasionally on an adjacent LB15 as well?
Do you have any other ideas if motor checks out ok?

[RLMTS]

As long a the DC bus stays above 240 DC from VH to VL you should be fine. It needs to be 300 DC (assuming 220 incoming), but if you incoming is at least 196 AC you should be fine. The ohm reading to ground sounds low. I would suggest borrowing a megger and double checking again. If less than 10 meg the motor is shorted, less then 100 meg the motor is damage the drive.

Hello Old Timer... after reading your response a second time, it appears that our situation does not fulfil your minimum requirements for DC bus voltage?
"It needs to be 300 DC"
(Our bus measures 288 DC)
Can you elaborate please.

PS Will be checking motor later today.

[Henrik Adler]

Hi
The LV lamp will always be on, if the system detects an error, because the powersupply will be turned off for security reasons.. Check to see if it is also on at the other drives.
If You can make it Work after having it turned og for a longer time, You probably have a problem at the lower board. (Internal powersupply) Have someone change all the electrolytic capacitors, and it will probably Work Again.

Best
Henrik

[RLMTS]

Thanks Henrik,
Do you mean the unit shown in the photograph? Or power section of drives?
-

[RLMTS]

Hello Henrik,
Can you please confirm which pcb you are referring to.
Thank you.

[Henrik Adler]

Hello Henrik,
Can you please confirm which pcb you are referring to.
Thank you.

If You take away the top board , You will see the NeXT board with 3 big transformers at the bottomn and a lot of capasitors.
Change the capasitors

Best
Henrik

[RLMTS]

Thanks Henrik.

[KMWPAT]

RMLTS, did changing the capacitors solve your problem? If so can you specify exactly where they are located?

Thanks,
KMWPAT

[Henrik Adler]

Just change all of them at the driver board. Also check if one or more of the 3 big power transistors at the bottom is shorted, They'
tend to blow off if the capacitors at the drive board are defect.

Best
Henrik

[Nperez40]

Greetings. I have an Okuma LB10 lathe with OSP 5000 control, a few months ago I had the same problem, the machine generated an amperage alarm on the z axis, the solution was to remove the control card, after a very detailed inspection I saw that most of condensers were inflated, the solution was to change all the condensers. after this the machine worked very well. I hope my experience helps you. Greetings from Colombia