Troubleshooting Faults of FANUC Alpha Servo Drives
This troubleshooting guide is in reference to Fanuc drives that begin with part number A06B-6079, A06B-6080, and A06B-6096 and is meant to help troubleshoot Fanuc alpha drive faults. If a drive status alarm appears on the 7 segment display, where the “-” refers to drive not ready (Waiting for an Emergency Stop signal to power up) and “0” refers to drive powering up correctly. Any other number or letter on this status display is an alarm code. One of the more common faults is an Alarm 8.i Here are some tips to check to see what the issue may be when an alarm comes up on your drive.
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1 – Check the link: (A06B-6079 drives only). An A06B-6079 drive can give a fault if the S1 Link is in the wrong position, so check the S1 – JV Connections (Type A Interface) and S2 – JS Connections (Type B Interface). An incorrect setting will cause an Alarm “8”.
2 – Check the wiring: A L motor is wired in the lower terminals and an M motor is wired in the upper terminals, both as U/V/W/E. JV1B connected from the L command plug of the axis card, JV2B from the M command plug. JX1A connected from previous drive, JX1B connected to the next drive in the line. The last drive in the line has a terminator in JX1B. 24v/0v/ESP connected into CX1A from the previous drive, out of CX1B to the next drive in the line.
3 – Disconnect motor cable: Meggar the motor to check the readings.
4 – Power machine on Do this while it is in an emergency stop. The drive is faulty if an alarm occurs, expect a “-” reading.
5 – Release Emergency Stop: Power the machine up after releasing the stop. If an alarm occurs, power the machine off and remove motor wires U/V/W/E (Note – this is dangerous on a vertical axis, brake release, slide drops etc). Release Emergency Stop and power the machine up. The drive is faulty if the alarm occurs, expect “0” reading.
6 – An additional test can be performed for equally sized 6079/6080 amplifiers H201 SVM2-12/12 H301 SVM2-12/12/12 H203 SVM2-20/20 H302 SVM3-12/12/20 (L&M) H206 SVM2-40/40 H303 SVM3-12/20/20 (M&N) H208 SVM2-80/80 H304 SVM3-20/20/20 (L/M&N) The suspect axis can be run from the other amplifier in the drive ie X drives M amplifier, Y drives L amplifier. To do this swap round a – X & Y Motor cables U/V/W/E (at the drive) and b – X & Y Command cables (at the drive) (6096 requires parameters changing to swap X & Y round).
The drive is faulty if the alarm remains the same as before the test. For example Alarm “8” is reported on a 6079-H201 drive using JV connections Steps 1~5 above, have been performed and still alarm “8”. Remove the servo motor wires from the lower terminals and reconnect into the upper terminals, upper into lower. Remove JV1B and insert into JV2B, JV2B into JV1B. Retest the machine.
The drive is faulty if the same alarm occurs, ie alarm “8” The fault lies elsewhere on the machine if another alarm occurs, ie alarm “9”. In this example the drive has detected an overcurrent from the L axis, alarm “8” Swapping the cables over allowed a different amplifier to control the axis. An “8” alarm would remain if the same drive circuitry detected the overcurrent. A “9” would occur if the overcurrent was detected using the other drive circuitry in the amplifier and the fault would be caused externally from the drive.