Old Hand Fault Finder

Allen-Bradley PowerFlex 525 F021: Output Phase Loss

Cites the manual · line-by-line check pending

What it means One output phase to the motor is open.

Likely causes

  • Loose motor lead
  • Failed contactor between drive and motor
  • Open winding

Checks, in order

  1. Check terminals and any output contactor
  2. Measure winding resistance

Source

Source (reworded, not copied): Rockwell Automation, PowerFlex 520-Series AC Drives User Manual, publication 520-UM001O-EN-E (September 2025), Chapter 4 Troubleshooting. Official manual (PDF). Fault numbers and names can differ between firmware versions.