Troubleshooting a COF (Current Offset) Fault
Topic Description

A COF fault indicates the drive attempted to adjust the current offset value beyond the allowable range due to residual induction current already present in the motor when the drive attempted to run the motor.

Possible causes:

  • A restart of the motor was attempted while the motor was coasting to a stop.
  • The internal current sensor (DCCT) is damaged.
  • A loose connection is present.
Resolution

COF occurring on startup due to a free-spinning motor:

  • If Speed Search is NOT required, create a motor restart sequence that allows enough time for the residual induction voltage to dissipate.
  • To enable Speed Search, follow the steps below:
    1. Set b3-01 = 1 to automatically enable Speed Search at start.
    2. Set b3-24 = 1 to set the Speed Search Method to Speed Estimation Type.
    3. If Speed Search needs adjusting, refer to Tips for using different Speed Search methods on a 1000 Series drive

COF occurring intermittently or on startup WITHOUT the motor free spinning.

  1. Remove power to the drive and wait at least 15 minutes to allow the capacitors to discharge. 
    • Caution: It is recommended to verify 10VDC or less is present on the DC bus before performing any service work.
  2. Check for loose connections or reseat connectors on the DCCT terminal connectors on the gate drive board and on the actual DCCTs. 
    • Note: NOT applicable on smaller drives (40HP and smaller).
  3. Verify the DCCTs are clean and not covered with dust or external residue of any kind.
    • Note: On smaller models, the DCCTs are built into the gate drive board. 
  4. Disconnect the motor leads from the drive.
  5. Apply power to the drive.
  6. Run the drive in either HAND/LOCAL or AUTO/REMOTE. If COF appears without the motor leads, the drive will need to be repaired or replaced. 
Related Documents
Setting Up and Using Speed Search

Product Types
A1000, A1000 Configured, iQpump1000, iQpump1000 Configured, P1000, P1000 Bypass, P1000 Configured, V1000, V1000-4X, Z1000, Z1000 Bypass, Z1000 Configured,
All Applications
Advanced Random Rotary Knife with Cam Blend, Air Compressor, Blister pack Thermoformer, Cartoner, Centrifuge, Conveyor, Crane/Hoist, Dynamometer, Elevators and Escalators, Extrusion, Fans/Blowers, Feed To Length, General Machinery, HVAC, Irrigation, Labeler, Laundry, Linear Flying Shear, Machine Tool, Mixer, Other, Packaging, Palletizer, Precision Grinding, Pump, Punch Press, Rotary Knife, Rotary Placer, Rotary Table Indexer, Screw Feeder, Semiconductor, Solar Cell Tabbing and Bussing, Solar - Textured Etching, Synch-Belt, Textile, Winding,
Last Modified Date: 11-13-2023ID: 10615