F091Type 2 fault (manual reset) · Encoder / feedbackUsually repairable
PowerFlex 525 F091: Encoder Loss
What F091 means
One channel of the encoder signal is missing. The drive needs a differential (A, A-not, B, B-not) encoder to check this.
Symptoms
Trips on start or while running when the drive uses encoder feedback or positioning.
Is it repairable?
Yes: encoders are repaired or replaced and cables rebuilt.
Common causes
- Broken or loose encoder wire
- Poor shield grounding
- Encoder power missing
- A failed encoder
Safe checks
- 1Check the encoder wiring and shield at both ends
- 2Measure the encoder supply
- 3With positioning, make sure the channels or motor leads are not swapped
Drives hold dangerous voltage after power-off. Checks should only be done by qualified personnel, with power isolated and the DC link discharged.
Reviewed by AutomIQ repair technicians. Code and name from the PowerFlex 520-Series Adjustable Frequency AC Drive User Manual.
Related PowerFlex 525 faults
- F004UnderVoltage
- F005OverVoltage
- F007Motor Overload
- F008Heatsink OvrTmp
- F012HW OverCurrent
- F013Ground Fault