How to Diagnose a FANUC High Current Alarm

[Note: A 414 alarm indicates you need to look at your servo drives or servo modules. If after looking at the drives or modules you find an HC LED lit or an 8, 9, A (or 12 for spindle) on the seven segment display, then you have a high current alarm. Solving for a high current alarm can be tricky because the problem may be caused by the motor, drive, or cable.]

Disconnect the four motor leads from the drive.

Power up and see if you have the HC alarm LED lit.

(ALARM CAN BE HC LED, ALARM 8/9/A/b (SERVO), or ALARM 12 (SPINDLE)

If you no longer get the HC alarm, then your motor is probably bad. Note: Spindle HC alarms will not show up until you try to move the motor with a very low speed M command.

If you still have the HC ALARM, then your drive is probably bad. However, we don’t know what caused the drive to fail.

By measuring through the four disconnected motor leads, you can check the power cables and the motor at the same time.

FIRST: With an ohm meter, check for shorts in the motor by measuring leg-to-leg and leg-to-ground on all three legs.
Leg-to-leg readings should be low, but consistent, on all three legs. The leg-to-ground readings should be open, or OL, on all three legs-to-ground.

SECOND: With a megger, check each leg-to-ground. The reading should show infinity (or 500 MEG and above) at the 1000V setting.

Check all three legs-to-ground because the problem can be in the power plug/terminal box of the motor or the power cables going from the drive to the motor.

AN OHM METER WILL TELL YOU IF YOUR MOTOR IS SHORTED.
A MEGGER WILL TELL YOU IF YOUR MOTOR IS GROUNDED.

See the link below if you do not have a megger. Recommend a 1000v, 2000 meg megger.
http://www.testequipmentdepot.com/bk-precision/insulation/308a.htm
© 2015 Tennessee Industrial Electronics (TIE) – FanucWorld.com

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