SV0441

Check Current Offset Values

Power on the control in emergency stop mode. Navigate to DIAGNOSIS > SERVO > CURRENT and observe the current offset for the affected axis. Normal values should be between -50 and +50; values exceeding ±200 indicate a detection circuit issue.

Take a screenshot or note the exact offset values over a 30-second period to detect fluctuations.

Ensure emergency stop is engaged to prevent unexpected axis movement.

Swap Servo Amplifier

Power off the machine, apply LOTO, and swap the suspected amplifier with a known-good unit from an identical axis or a compatible spare. Power on and check if the alarm follows the amplifier. If it does, the original amplifier is faulty.

Label amplifiers before swapping to avoid mix-ups, and double-check parameter compatibility.

Ensure mechanical brakes are engaged during swap to prevent axis movement.

Replace Faulty Amplifier

If the alarm follows the amplifier, replace it with a new or refurbished unit of the exact model. After replacement, perform servo tuning via MAINTENANCE > SERVO > AUTOMATIC ADJUSTMENT to recalibrate the system.

Keep a spare amplifier on hand for critical axes to minimize downtime.

Verify firmware and parameter settings match the original amplifier to avoid mismatches.

Visual Cable Inspection

Power off the machine, apply LOTO, and inspect the motor power cables at both the amplifier and motor ends. Look for frayed wires, burnt terminals, or loose connections at U/V/W terminals.

Use a flashlight to check for subtle cracks or discoloration in insulation near connectors.

High voltage may be present; ensure LOTO is strictly followed.

Test Cable Continuity

Using a multimeter, test continuity of each phase (U, V, W) from amplifier to motor. Also, check shield continuity and ensure proper grounding to the PE terminal. Any open circuit or high resistance indicates cable damage.

Wiggle the cable during testing to detect intermittent breaks.

Disconnect cables from amplifier before testing to avoid false readings.

Replace or Repair Cable

If damage or poor continuity is found, replace the motor power cable with a new one of the correct specification and length. Secure all connections tightly and retest for continuity before powering on.

Route new cables away from heat sources or sharp edges to prevent future damage.

Use only manufacturer-approved cables to ensure proper shielding and current capacity.

Disconnect Motor Cables

Power off the machine, apply LOTO, and disconnect the motor power cables from the servo amplifier terminals to isolate the motor for testing.

Label cables before disconnection to ensure correct reassembly.

Do not test with amplifier connected; risk of damaging electronics.

Test Insulation Resistance

Using a megohm meter at 500V DC, test insulation resistance between each motor phase (U, V, W) and ground. Readings should be >10MΩ; anything below 1MΩ indicates a ground fault.

Perform the test in a dry environment to avoid false low readings due to moisture.

Ensure no residual charge remains in motor windings before testing.

Test Phase Balance and Replace Motor

Measure resistance between phases (U-V, V-W, W-U); all values should be within 5% of each other. If imbalance or low insulation is confirmed, replace the motor and perform servo tuning after installation.

Document resistance values for future reference during periodic maintenance.

Handle replacement motor carefully to avoid mechanical damage during installation.

Inspect Feedback Cable Shielding

Power off the machine, apply LOTO, and inspect the motor feedback and power cables for damaged shielding or exposed wires that could pick up electrical noise.

Look for areas where cables pass near high-power lines or inverters, which can induce noise.

Ensure power is fully isolated before handling cables.

Verify Grounding Integrity

Check that the amplifier chassis and motor are properly grounded to the machine’s PE terminal. Use a multimeter to confirm low resistance (<1Ω) between grounding points.

Tighten all grounding screws and clean contact surfaces to ensure solid connections.

Poor grounding can pose a shock hazard; verify before proceeding.

Reroute or Replace Cables

If shielding damage or grounding issues are found, replace affected cables or reroute them away from noise sources like power lines or inverters. Retest for alarm after corrections.

Use ferrite cores on feedback cables near the amplifier to suppress high-frequency noise.

Ensure replacement cables meet OEM specifications for shielding.

Check Amplifier Temperature

Power on the machine in emergency stop mode and navigate to DIAGNOSIS > SERVO > TEMPERATURE. Verify that the amplifier temperature is below 50°C at idle. Higher readings indicate overheating.

Monitor temperature trends over 10 minutes to detect rapid increases.

Do not touch amplifier components; they may be hot even at idle.

Inspect Cooling System

Power off, apply LOTO, and visually check the amplifier cooling fan for operation and airflow. Clean any dust or debris from vents and ensure no obstructions are present.

Use compressed air to clean vents, but avoid excessive pressure that could damage components.

Ensure machine is powered off before cleaning to avoid fan-related injuries.

Improve Cooling or Replace Fan

If the fan is faulty or temperature remains high, replace the fan or improve cabinet ventilation. Retest temperature after corrections and monitor for alarm recurrence.

Consider adding auxiliary cooling if ambient temperature in the control cabinet exceeds 40°C.

Use only compatible replacement fans to ensure proper airflow.