troubleshooting servo alarms

GE Fanuc Automation__________________________________________________________________________________

Troubleshooting Servo Amplifier Alarms

March 1999


TABLE OF CONTENTS

1. CORRECTIVE ACTION FOR FAILURES..................................................................................3

1.1 ALPHA SERIES SERVO AMPLIFIER UNIT FRONT PANEL................................................................41.2 BETA SERIES SERVO AMPLIFIER UNIT FRONT PANEL..................................................................51.3 ALPHA SERIES SERVO AMPLIFIER INDICATORS............................................................................61.4 BETA SERIES SERVO AMPLIFIER INDICATORS..............................................................................6

2. TROUBLESHOOTING SERVO ALARMS..................................................................................7

3. RECOVERY PROCEDURES........................................................................................................8

3.1.1 LED INDICATIONS AND MEANINGS.........................................................................................83.1.2 ACTIONS TO BE TAKEN ON EACH ALARM............................................................................10

4. TROUBLESHOOTING SERVO MOTORS................................................................................15

5. RELATED GE FANUC MANUALS............................................................................................16


1. Corrective Action for Failures

When a failure occurs, it is important to correctly grasp what kind of failure occurred and take appropriate action, to promptly recover the machine.

Check for the failure according to the following procedure:

When? With what operation? What failure?

Grasp the kind of failure

Appropriate Action

Recovery


1.1 Alpha Series Servo Amplifier Unit Front Panel


1.2 Beta Series Servo Amplifier Unit Front Panel


1.3 Alpha Series Servo Amplifier Indicators

LED Digital Display: This display will show a number or symbol to indicate amplifier status or errors. This information is also sent to the control. If no errors are sensed by the Amplifier, this display will contain either a zero (0) symbol, indicating the amplifier is ready, or a dash (-) symbol, indicating that it is waiting for an enabling signal (“MCON”) from the control. A troubleshooting chart based upon this display is presented in this write-up.

DC Link Display: This red-colored LED lights whenever a voltage level is present on the DC Link high voltage supply inside the Amplifier. Since this voltage is filtered by a large capacitor, this LED may remain lit for several minutes after power is turned off while the capacitor discharges.

1.4 Beta Series Servo Amplifier Indicators

The Beta Servo Amplifier has four LED indicator lights on its front panel as shown on the previous layout drawing. The functions of these LEDs are summarized in the chart below.

Beta Servo Amplifier LED IndicatorsLED Function

Power When lit, indicates that the 24 VDC input power is appliedReady When lit, indicates that the amplifier has been activated (“drive

enabled”) by the control and is ready to run the motor. ALM When lit, indicates that the control has sensed an error.Charged When lit, indicates that the DC Link power supply is charged.

Charged (DC Link) LED: This red-colored LED lights whenever a voltage level is present on the DC Link high voltage supply inside the Amplifier. Since this voltage is filtered by a large capacitor, this LED will remain lit for approximately two minutes after power is turned off while the capacitor discharges


2. Troubleshooting Servo Alarms

This part describes troubleshooting. Each item should be carefully followed to find the cause of trouble and take necessary actions. First, check the alarm No. (displayed on the HMI alarm screen) and the status indicator in the servo amplifier unit to find the cause of the problem. Second, take the appropriate actions described in Chapter 3.


3. Recovery Procedures

3.1.1 LED Indications and Meanings

If an alarm condition related to the servo amplifier unit occurs, the 7-segment LED indicator on the amplifier front panel behaves as listed below.


3.1.2 Actions To Be Taken On Each Alarm


4. Troubleshooting Servo Motors

Before replacing a motor, a reasonable effort should be made to be sure that it is truly defective. The troubleshooting procedures in the Amplifier Error Detection Alarm chart, found earlier in this section, should be followed in an effort to pinpoint the cause of a problem. If the evidence points to a defective motor, the following basic checks can be performed:Ohmmeter Check

1. Turn control power off and use applicable lockout and safety procedures.

2. Label or make a note of the wiring connections for the three motor connection leads on the amplifier’s T1 terminal strip, terminals U, V, and W.

3. Disconnect the three motor leads from these terminals.

4. Use an ohmmeter, preferably a high quality digital type, on its lowest resistance range to measure the resistance between all three motor lead-pair combinations: U to V U to W V to W

5. The three resistance readings should be equal within 5%. If not, disconnect motor cable only (if you disconnect the encoder cable, it will be necessary to reference the axes) from motor and repeat check at the motor to see if abnormal reading is in the cable or the motor. Replace the defective item.

6. Change to the highest resistance range on the ohmmeter and measure the resistance between each motor lead and ground (ground is on terminal 12 of terminal strip T1). All three resistance readings should be at least 20 megohms. If not, disconnect motor cable only from motor and repeat check to see if abnormal reading is in the cable or the motor. Replace the defective item.

Ammeter Check

1. If the ohmmeter readings are normal, and it is possible to run the motor, which might be the case with an intermittent problem, reconnect the motor leads as at the start of this procedure, then turn power back on and run the motor through a safe test sequence while taking amperage readings on all three motor leads with a clamp-on ammeter. Ammeter readings should be equal (within reason) and below the maximum motor rating. If any reading is abnormally high, check the voltage balance between AC input phases. If phase voltages are equal, within reason, but an ammeter reading is high on one or two legs, suspect a defective motor.

GE Fanuc Automation__________________________________________________________________________________ 2. It should be noted that high friction caused by a mechanical defect in the

attached equipment could result in high current readings, but they would probably be high on all three motor leads. If you have compiled a record of “normal” ammeter readings as suggested in the Preventive Maintenance section, compare the measured readings with the recorded ones to help in assessing the situation.

5. Related GE Fanuc Manuals

Series Amplifier (Servo Amplifier Unit) Maintenance Manual, GFZ-65195 PowerMate H Maintenance Manual, GFZ-62685

troubleshooting servo alarms

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