E.OC / EOC fault in KEB COMBIVERT F5 Drive

Categories: Faults & Alarm

E.OC / EOC fault in KEB COMBIVERT F5 Drive indicates an Over Current. This means the inverter’s output current spiked beyond the permissible peak limit or a ground fault occurred.
Cause:

  • If the error occurs instantly at the start of each run:
    • Ground fault on motor leads.
    • Damaged or slow to close motor contactor.
    • Shorted output transistor.
    • Motor failure.
  • If the error is intermittent:
    • Damaged or slow to close motor contactor.
    • Loose motor connections.
    • Electrical noise, faulty grounding.

Remedy:

The current and peak current may be viewed in LF.93 and LF.94. To reset the logged peak value, press enter.

Systematic Isolation & Checks:

  • To determine if the over current is caused by the inverter, motor, or intermediate components (e.g. motor contactor), systematically isolate these items.
  • Bypass testing: Start by bypassing the motor contactor (do not simply jumper!).
  • Resistance checks: Perform checks with the motor disconnected from the inverter. Measure resistance from phase to phase (should read winding resistance specified by manufacturer). Measure phase to ground resistance (should read open circuit). If a fault is indicated, disconnect cables at the motor side and remake the test to isolate motor vs. cabling.
  • Insulation tests: Meg tests to check motor winding insulation can only be performed with the motor completely disconnected from the inverter to prevent high-voltage damage to the output section of the drive.
  • Inverter output testing (Open-loop mode):
    1. Power off, wait for appropriate discharge time, and disconnect motor leads from the inverter.
    2. If not an induction motor, change the motor configuration to induction motor in US10 (note existing settings before doing this, as changing this parameter will default all parameters), then Write Configuration to Drive in US04.
    3. Set LF.30 Control Mode = Open Loop V/Hz.
    4. Run the system with the motor leads disconnected in open-loop. If the overcurrent error still occurs, the inverter output is faulty. If it does not occur, the fault lies in the motor, cabling, or contactor.

Note: Under normal operation, the drive limits the output current to the maximum torque in 0.LF36 (Maximum Output Current = LF.12 Motor Current × 0.LF.36 Maximum Torque / LF.17 Motor Torque). The drive also limits output current to the hardware current limit listed as Peak Current (30sec.) rating in the Technical Data tables (Sec. 2.1 and 2.2).