KUKA KRC4 Error Code 120

KUKA Robot Major Motor

Model: KRC4 | Code: 120

Applicable Systems
KR CYBERTECH

Symptoms

Motor stalled. The robot motor has stalled. Zero speed is detected while a motion command is active andtorque is being applied.

Possible Causes

  • Excessive payload exceeding motor torque capacity
  • Mechanical jam or collision with obstacle
  • Brake not releasing, preventing motor rotation
  • Motor phase loss: one winding open circuit
  • Gearbox seizure or bearing failure

Troubleshooting Steps

  1. Step 1: Check the equipment status and fault indicators to confirm the active fault code
    Fault indicator or HMI displays code 120 as active
  2. Step 2: Verify all electrical connections, wiring harnesses, and connector seating
    All connections secure, no corrosion, loose pins, or damaged wires
  3. Step 3: Check motor cable connections at drive output terminals for correct phase sequence and tightness
    Cables securely connected, phase sequence correct, no loose terminals
  4. Step 4: Measure motor winding insulation resistance with a megger (500V DC minimum)
    Insulation resistance above minimum value (typically > 1 Megaohm)
  5. Step 5: Verify drive parameter settings match motor nameplate data (current, voltage, power, RPM)
    All motor nameplate parameters correctly entered in drive
  6. Step 6: Inspect motor for mechanical overload, bearing seizure, or driven equipment jam
    Motor rotates freely, no mechanical binding or excessive load
  7. Step 7: Reset the fault after fixing the root cause: clear the fault via HMI or power-cycle
    Fault clears and drive resumes normal operation without recurrence

How to Reset

To reset: 1) Identify and fix the root cause described in the fault symptoms. 2) Press RESET on the HMI or controller, or power-cycle the equipment. 3) If the fault recurs, contact manufacturer service. Caution: Document the fault code and context before resetting.

Frequently Asked Questions

  • Q: What does fault code 120 mean on the KUKA KRC4?

    Fault 120 on the KUKA KRC4 indicates: Motor stalled. The robot motor has stalled. Zero speed is detected while a motion command is active and torque is being applied. Refer to the equipment manual and manufacturer support for specific troubleshooting steps.

  • Q: Can I continue operating the equipment with fault 120 active?

    No. The equipment has detected a fault condition and has taken protective action (typically stopping or derating). Continuing to operate without fixing the root cause may cause further damage. Always investigate and fix the fault before resuming operation.

Related KUKA Fault Codes

Source: KUKA Robot Controller KRC4 Operating Manual, KUKA Roboter GmbH Documentation

Category: Robot