Applicable Systems
MoviDrive

Symptoms

Speed deviation. The actual motor speed deviates from the commanded setpoint speed beyond the configuredtolerance for longer than the allowed time.

Possible Causes

  • Excessive load causing motor to slow below speed tolerance
  • Speed feedback encoder signal degraded or intermittent
  • Speed controller gain parameters incorrectly tuned
  • Mechanical binding or jam in the driven equipment

Troubleshooting Steps

  1. Step 1: Check the equipment status and fault indicators to confirm the active fault code
    Fault indicator or HMI displays code F21 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 encoder cable and connector at both motor and drive/controller ends
    Cable intact, connector fully seated, no bent or corroded pins
  4. Step 4: Verify encoder signal integrity with an oscilloscope if available
    Signal waveform normal with clean edges, no dropouts or noise
  5. Step 5: Check for mechanical interference, coupling slippage, or excessive load on the axis
    No mechanical interference, coupling secure, load within rated capacity
  6. Step 6: Verify the axis reference point and home position are valid
    Axis has valid reference point, position data is consistent
  7. Step 7: Replace encoder if signal is consistently absent or corrupted after cable checks
    New encoder provides stable, clean signal

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 F21 mean on the SEW Eurodrive MoviDrive?

    Fault F21 indicates a position or encoder-related fault. The control system has detected an issue with axis positioning, speed feedback, or encoder signal. Check the encoder cable and motor feedback system.

  • Q: Can I continue operating the equipment with fault F21 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 SEW Eurodrive Fault Codes

Source: SEW Eurodrive MoviDrive MDX61A Operating Instructions, SEW-Eurodrive Documentation

Category: PLC & VFD