A servo drive converts control commands into accurate motor movement for position, speed, or torque. Problems can come from power, feedback, communication, or heat issues. Start troubleshooting by checking the active fault code, then review power, wiring, feedback, communication, and mechanical parts. This order helps technicians find the cause, fix it, and make sure everything works right.

What Is a Servo Drive and How Does It Work?

A servo drive changes command signals into motor movement by controlling position, speed, or torque. It works with power electronics, control circuits, feedback, and a communication interface. Servo systems often use closed-loop feedback for precise motion, while Variable Frequency Drives (VFDs) are usually used to control motor speed and torque.

Why Servo Drives Fail: The Root Causes

Servo faults can result from several operating conditions, including:

  • Power Instability: Overvoltage, undervoltage, or missing phases.
  • Communication Failures: EtherCAT, PROFINET, or EtherNet/IP mismatches.
  • Feedback Problems: Encoder, wiring, or connection issues.
  • Mechanical Issues: Binding or misalignment.
  • Parameter Settings: Incorrect gain or motor settings.
  • Thermal Conditions: Overheating or excessive load.

Looking at these areas can help you find the most likely cause of the problem.

8 Common Servo Drive Problems and How to Fix Them

To troubleshoot, match the symptoms to possible causes and follow the steps in the manufacturer’s guide:

1. Fault or Alarm Code Displayed on Startup

If you see an alarm at startup, it could mean there is a problem with the power supply, wiring, connections, or settings. Write down the fault code, check the input voltage and phases, look over the connections, and follow the manufacturer’s reset steps after fixing the issue.

2. Drive Is Powered On, but the Motor Won’t Move

The drive might be turned off, missing a command signal, or getting the wrong feedback. Check if Run or Enable is active, make sure the PLC wiring and commands are correct, and look at the feedback connection.

3. Overvoltage Error

Overvoltage when slowing down can happen because of energy sent back to the system, high supply voltage, or stopping too quickly. Check the supply voltage, look at the braking resistor or regenerative system if used, and adjust the deceleration settings as the manufacturer recommends.

4. Undervoltage Error

Undervoltage can be caused by low supply voltage, drops in voltage, loose connections, or issues with the power supply. Check the incoming voltage and all connections, then look at the power supply parts as the manufacturer suggests.

5. Overcurrent Error

Overcurrent can happen if there is too much load, something is stuck, the motor has problems, settings are wrong, or the motor and drive do not match. Check the bearings, rails, and couplings, test the motor as the manufacturer recommends, and make sure the motor and drive work together.

6. Encoder or Feedback Error

Encoder or feedback alarms can be caused by damaged cables, loose connections, dirt, misalignment, or problems with the encoder. Check the wiring and connectors, make sure everything is lined up, and test the feedback device as the manufacturer advises.

7. Communication Error With the PLC

If communication with the PLC stops, it might be due to damaged cables, wrong network settings, protocol issues, or electrical noise. Check the communication cables, make sure the network and protocol settings are correct, and look at grounding and shielding.

8. Overheating or Thermal Overload

Thermal alarms can happen if there is not enough airflow, the cooling fan is not working, the area is too hot, the load is too high, or the system is working too hard. Clean the cooling surfaces, check the fans and airflow, and make sure the system is running within the manufacturer’s limits.

Abnormal Noise and Excessive Vibration: What They’re Telling You

A steady hum is usually normal, but strange squealing or whining sounds can mean the bearings are worn, there is dirt, the load has changed, or something else is different. Compare these sounds to normal operation to spot changes that need checking.

Too much vibration can mean the bearings are worn, the motor and load are not lined up, the shaft is bent, the rotor is unbalanced, or something is loose. Check these parts to find the problem and fix it.

Servo Drive Troubleshooting Checklist Before You Call for Repair

Before arranging repair, complete these checks:

  • Fault Code: Record active display or LED alarms.
  • Power Supply: Measure voltage and confirm all phases.
  • Cables: Inspect power, encoder, and communication cables.
  • Run Mode: Confirm Enable mode and command signal.
  • Cooling: Check fans, heat sinks, and airflow.
  • Parameters: Compare settings with the last known-good backup.
  • Operation: Check for abnormal noise and vibration.
  • Documentation: Review the manufacturer’s fault-code manual before replacing parts.

Doing these checks will help you decide what to do next.

Preventive Maintenance Tips to Reduce Servo Drive Faults

At ElectroCraft, we recommend these preventive maintenance practices:

  • Cooling: Inspect fans and ventilation on schedule.
  • Connections: Tighten terminals and grounding points.
  • Monitoring: Track vibration and temperature trends.
  • Cleaning: Remove cabinet dust and contamination.
  • Backups: Back up parameters and record firmware versions after approved changes.
  • Capacitors: Inspect and replace capacitors according to manufacturer recommendations.
  • Training: Follow correct startup and shutdown procedures.

Following these steps helps your equipment run smoothly and reliably.

When to Repair vs. Replace a Servo Drive

Repair can be practical when parts and Original Equipment Manufacturer (OEM) support remain available. Consider replacement when:

  • Repeated Failures: The drive has recurring hardware issues.
  • OEM Support: Support or firmware updates have ended.
  • Parts Availability: Replacement components are unavailable.
  • Downtime Cost: Downtime exceeds repair costs.
  • Communication Standard: The standard no longer fits the current control architecture.

Thinking about these factors will help you make smart choices about repair or replacement.

Servo Drive Fault Codes by Brand: Quick Reference

Different manufacturers and models use different fault terms. Common types include:

Brand Example Fault Category Typical Area to Check
Yaskawa Sigma-7 Encoder or regenerative alarms Feedback or regenerative circuit
Siemens SINAMICS S120 DRIVE-CLiQ or encoder faults Communication or encoder
Mitsubishi MR-J4 Encoder communication errors Encoder, cable or feedback
FANUC Servo or Pulsecoder alarms Servo or feedback
Allen-Bradley Kinetix DC bus or feedback faults Supply or feedback

Confirm the exact code, cause, and corrective action in the model-specific manufacturer manual.

Conclusion

To troubleshoot well, start by checking fault codes, power, feedback, communication, temperature, and mechanical parts. Regularly inspect cooling, connections, settings, and how the system is running to keep things reliable. At ElectroCraft, we suggest following the manufacturer’s advice, keeping service records, and using a step-by-step process to decide on repairs or replacements.

FAQs

What does it mean when a servo drive shows a fault code?

A fault code identifies a detected operating condition. Refer to the manufacturer’s manual for its meaning and corrective action.

Can a servo drive be repaired, or does it need to be replaced?

Many drives can be repaired. Replacement depends on condition, component availability, manufacturer support, compatibility, and repair feasibility.

How do I know if the problem is the servo drive or the servo motor?

Use manufacturer-approved diagnostic procedures to test both components and identify which one is associated with the reported fault.

How often should servo drives be serviced?

Follow the manufacturer’s maintenance schedule, considering operating hours, duty cycle, temperature, contamination, vibration, and application conditions.