Alarm 8 Troubleshooting for FANUC CNC Servo Amplifier

Servo Amplifier Alarm 8, 9, A
CNC Alarm SV0600
Applies to Alpha i Servo
Alarm 8, 9, or A on the Alpha i servo amplifier is a high current alarm.

Alarm SV 600 is generated by the CNC when it detects that an amplifier has a high current alarm. In parentheses, the alarm will indicate the axis that the amplifier controls. If it is a multiple-axis drive, you will get an alarm for each axis.

Unless you know exactly which amplifiers drive which axes, the best thing to do is access the electronics cabinet with power on (safely, please) and look at the status displays of the units while the alarm is occurring. You're looking for the unit that is displaying either an 8, 9, or A.

After you lock out the machine, pull out and plug back in the board that makes up the faceplate of the amplifier - the one with all the cables plugging into it. Oh I didn't mention locking the machine out yet?

The servo amplifiers are in the electrical cabinet and opening the cabinet with power applied potentially exposes you to danger.

In order to accurately troubleshoot the exact cause of this alarm, you will need to have power applied to the equipment. Don't attempt to perform anything discussed in this presentation if you are not both fully qualified to do so and have the equipment owner's permission to do so.

Once you are done troubleshooting and before performing any maintenance, follow all plant safety and lockout procedures. These procedures should include releasing all energies related to the maintenance procedure performed.

OK, why are we looking for three different indications? Alarm 8, 9, and A are all the same problem, the difference is which amplifier axis the alarm exists on.

8 is for the first axis which is labelled L on the amplifier

9 is for the second axis which is labelled M on the amplifier

A is for the third axis, labelled N

So if your amplifier only controls two axes, like the one shown here, it should definitely never pop up an A.

Now that you know which amplifier is alarming out, let's figure out what the trouble is. With this alarm, you basically have a short to ground. The short is causing too much current to flow through the power module inside the amplifier and will eventually break it, if it hasn't already.

On most machines the amplifiers turn on when you turn on the main breaker and then you press the ON button to turn on the CNC and bring the servo system online.

If you turn on the breaker, leave the CNC turned off, and the servo amplifier has this alarm right away - it's almost fixed. Unplug the feedback connector to the amplifier axis that the alarm is on and try it again. If the alarm goes away, you have a problem with the feedback cable or the pulsecoder it goes back to.

If the alarm is still there with the cable unplugged, the amplifier is bad. In a little bit I'll discuss checking the motor and power cable, you should do that too but you definitely need a new amp.

If the alarm only comes up once the CNC is turned on, keep looking for the problem.

The next thing to do is disconnect the motor power leads from the amplifier.

They're plugged into the bottom.

If you are removing the motor power for a vertical axis, make sure you physically prop that axis up because we're about to make it fall out of the sky.

With the motor power leads disconnected, turn on the CNC and release any emergency stop condition. With e-stop released, servo motor brakes will release too so hopefully you didn't skip the 'prop up the axis' step.

If the drive displays the high current alarm again, replace it, you know it's bad. The motor needs to be checked as well to see if it's what broke the amp.

No alarm is a decent sign but doesn't give the amp a clean bill of health yet.

Now we'll check the Intelligent Power Module, or IPM, in the amplifier. This is what delivers the current to the motor. You will make 6 checks.

With power locked out and the DC link completely discharged, measure resistance with a standard multimeter from the top bus bar connection to each of the motor power pins on the bottom of the amplifier. You should read hundreds of K ohms up to wide open. You may find using a lead with a clip makes it slightly easier.

You're going to check between the top bus bar and all three pins that connect to the motor power. If the three readings are not balanced, let's say within 10% of each other, the IPM is bad which basically means the amp is bad. You might see two readings with high resistance and one with a short - that's a bad IPM. Maybe it's not a short but it's just much lower resistance - that's a bad IPM.

Next, move your lead from the top bus bar connection to the bottom one and check resistance of the three motor power pins again. You're still looking for high resistance but it will be in the tens of K ohm range instead of hundreds.

You are still looking for the three readings to basically match each other. Any more than 10% variance should be considered bad.

Видео Alarm 8 Troubleshooting for FANUC CNC Servo Amplifier канала FANUC America Corporation