Having trouble with a KEB COMBIVERT F5 drive? Learn how to identify, troubleshoot, and reset E.xxx faults, A.xxx warnings, and watchdog errors.

When an abnormality is detected, the drive categorizes the event to help operators isolate the problem . On the drive's keypad or COMBIVIS software, status messages are classified using specific prefixes :

• Faults / Errors (E.xxx): Critical errors that immediately deactivate the drive's output modulation (pulse block), causing the motor to coast to a stop . The drive locks into this state and must be reset before a restart is allowed.
• Malfunctions / Alarms (A.xxx): Operational warnings that indicate an out-of-spec condition . Depending on the configuration, the drive’s reaction can vary, but it does not necessarily stop the motor immediately .
• Status Messages (No Prefix): Plain text or abbreviations indicating the active operating status of the inverter (e.g., constant forward run, standstill).

This technical guide explains how to read KEB F5 status codes, perform safe resets, and diagnose common faults to keep your machines running smoothly.

KEB COMBIVERT F5 Fault Codes Reference Table

Refer to your specific diagnostic reference table to identify the exact E.xxx or A.xxx code active on your KEB drive's keypad or diagnostic interface.

KEB COMBIVERT F5 Drive Fault Codes List

Error / Message and Description	Cause and Solution / Troubleshoot
E.OL2 Error Low Speed Overload Occurs if the low frequency, standstill constant current is exceeded (see Technical Data for stall current levels and overload characteristics). The error can only be reset if the cooling time has elapsed and E.nOL2 is displayed.	Cause: Excessive current at low speed (typically below 3Hz). Possible factors include: Incorrect motor data. Incorrect encoder configuration. High mechanical load/friction issues (e.g. starting or stopping against brake). Remedy: Verify motor data, specifically the motor rated speed and frequency relationship for PM Synchronous Motors. Verify correct encoder settings including: LF.27: Encoder Pulse Number LF.28: Swap Encoder Channels (A/B setting) LF.77: Encoder Pole position for PM Synchronous Motors. Relearn Encoder Pole Position as needed (see Section 5.11.1). Check for high mechanical load/issues (friction) such as starting or stopping against brake.
E.dOH Error Motor Overheat The external motor temperature sensor tripped.	Cause: If a motor PTC temperature sensor, relay, or KTY (special hardware required) is connected to terminals T1, T2 and the motor overheat function US.33 EdOH Function = On, then the relay opens when PTC resistance exceeds 1650 Ohms. Excessive motor heating causes may include: Excessive current. Incorrect encoder settings. High mechanical load/friction. Insufficient motor cooling. Remedy: Verify correct motor data. Verify correct encoder settings including: LF.27: Encoder Pulse Number LF.28: Swap Encoder Channels (A/B setting) LF.77: Encoder Pole position for PM Synchronous Motors. Check for high mechanical load/issues (friction). Inspect and ensure sufficient motor cooling.
E.OH2 Error Motor Protection Electronic Motor Overload protection was activated.	Cause: Excessive RMS motor current according to the LF.08 Electric Motor Protection overload curve, or if the LF09 Peak Motor Current Factor is exceeded for more than 3 seconds for PM Synchronous Motors. For induction motors, the baseline current for Electric Motor Protection corresponds to LM09 Electric Motor Overload Current. For PM Synchronous Motors, the baseline current corresponds to LF.12 Motor Current. Remedy: Verify motor data, specifically the motor rated speed and frequency relationship for PM Synchronous Motors (see Section 5.6.2). Verify correct encoder settings including: LF.27: Encoder Pulse Number LF.28: Swap Encoder Channels (A/B setting) LF.77: Encoder Pole position for PM Synchronous Motors. Relearn Encoder Pole Position as needed (see Section 5.11). Check for high mechanical load/issues (friction).
E.OC / EOC Error Over Current Occurs when the specified peak output current is exceeded or if there is a ground fault.	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): Power off, wait for appropriate discharge time, and disconnect motor leads from the inverter. 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. Set LF.30 Control Mode = Open Loop V/Hz. 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).
E.OP Error Over Voltage The DC bus voltage rises above the permissible value either during motor regenerative operation or as a result of line side voltage spikes. For 460V drives, the over voltage level is 840VDC and for 230V drives, the over voltage level is 400VDC. The over voltage level cannot be adjusted.	Cause: Elevated DC bus voltage. Common sources include: Motor regenerative operation (deceleration or overhauling). Transient voltage spikes from the mains supply. High line input voltage. Malfunctions in the DC bus voltage measurement circuit. High-frequency electrical noise. Remedy: The DC bus voltage LF.95 and the peak DC bus voltage LF.96 can be monitored. Braking Resistor Check: When using a braking resistor to dissipate regenerated energy, the braking resistor should come on at: 460V drives = 760VDC 230V drives = 380VDC Ensure proper connection of the braking resistor to the braking transistor terminals PB, ++. Disconnect the braking resistor and measure resistance to verify if correct. Check the braking transistor if problems persist. Line Regen Unit Check: If a line regen unit is used, by default, the line regen unit will turn on at 103% of the idle DC bus voltage. Ensure proper connection between the drive and regen unit at the ++ and - - terminals at both units. Ensure the regen unit is regenerating properly, is in the regen status when required, and has no active faults preventing operation. Transient Spikes: If the over voltage is due to transient voltage spikes from the line, install a 3-5% line reactor. High Line Voltage: Step-down the line voltage using a transformer. Measurement Circuit or Noise Issues: Measure the DC bus directly and verify against the DC bus voltage read from the Diagnostics screen. The DC bus should measure approximately 1.41 x AC Input phase-to-phase. If there is high-frequency noise, verify proper mains grounding.
E.PU Error Power Unit General power circuit fault.	Cause: Internal power circuit malfunction. Remedy: The inverter must be inspected and repaired by KEB or replaced.
E.PUCH Error Power Unit Changed The control card recognizes a new power stage (the control card was changed).	Cause: Control card change or hardware modification. Remedy: This error should automatically clear itself.
E.PUCI Error Power Unit Invalid During the initialization, the power circuit could not be recognized or was identified as invalid.	Cause: Initialization recognition failure. This error could occur from electrical noise. Remedy: Disconnect the terminal strip, encoder cable, and serial communication (if used), then power cycle the drive. Check phase-to-phase and phase-to-ground line voltages to make sure they are balanced and not causing noise. Re-seat the ribbon cable connecting the control card to the power stage.
E.UP Error Under Voltage The DC bus voltage drops below the permissible value. For 460V drives, the under voltage level is 240VDC and for 230V drives, the under voltage level is 216VDC. The under voltage level cannot be adjusted.	Cause: DC bus voltage drop. Common sources include: Input voltage too low or unstable. One phase of the line input is missing. Line input phases are imbalanced (the phase-to-phase voltage imbalance should not exceed 2%). Undersized or incorrectly wired isolation transformer. Faulty DC bus voltage measurement circuit. Remedy: Verify the input voltage and wiring. The DC bus should measure approximately 1.41 x AC Input phase-to-phase, and should match the DC bus measurement read by the drive in the Diagnostics Menu. Measure the DC bus directly and verify against the DC bus voltage read from the Diagnostics screen. Note: A 460V drive can operate on a 230V, single phase power supply if programmed for UPS mode operation.
nE.OL2 no Error Low Speed Overload No more overload.	Cause: Low speed overload has cleared. Remedy: The error is cleared and the drive can be reset.
nE.dOH no Error Motor Overheat Over temperature reset possible.	Cause: Motor temperature has dropped back to acceptable levels. Remedy: The motor overheat sensor is reset, and the Error Motor Overheat fault can be reset.
nE.OL no Error Overload No more overload.	Cause: The overload counter has reached 0%. Remedy: Allowing the motor to cool down to 0% overload allows the error overload to be reset.
no_PU Power Unit Not Ready Control card is powered up, but the power stage is not, and is not seen by the control card.	Cause: The Power Unit Not Ready message may occur due to: Control card powered up by an external power supply, but the drive is not powered up by the line. Since the drive is not being powered by the line, the power stage cannot be identified. Connection issues between the control card and the power stage. Failure of the switching power supply. Remedy: For inverter housing sizes G, H, R, U: Remove then reconnect the ribbon cable connecting the control card to the power stage at the control card connection. For inverter housing sizes D, E: Remove the control card then re-seat, ensuring correct pin connections. If reseating the ribbon cable does not resolve the issue, there may be a failure of the switching power supply. The drive will need to be replaced or inspected and repaired by KEB.
I_data Invalid Data	Cause: Parameter is outside of the permissible limits. Remedy: Ensure the parameter entered is within the permitted range.
I_oPE Invalid Operation	Cause: An operation was attempted in an incorrect state or while inputs are active. Remedy: Change the drive mode from Run to Stop. Check LF.82 input status to ensure no inputs are currently active.
EOH Error Overheat Power Module The heat sink temperature rises above the permissible limit.	Cause: The heatsink temperature can be viewed in ru.38. The overheat limit is 90 degrees Celsius for most drives (see Technical Data for units 175HP and larger). Under normal operation, the heatsink temperature should usually be below 65 degrees Celsius. Causes of inverter heatsink overheat include: Insufficient cooling or ambient temperature too high. Faulty temperature sensor. Remedy: Verify operation of fans: The fans are thermostatically controlled to come on at about 45 degrees Celsius. To turn all fans on high, US.37 Function Test can be set to "Fans On". Make sure fans are not clogged. Increase airflow around the inverter or add cabinet fans. Check sensor integrity: Power down the inverter or let it stand idle to allow for the heatsink temperature to cool. If the heatsink temperature read by the drive for diagnostics seems unreasonably high for a heatsink cool to the touch, the heatsink temperature sensor may be faulty and would need to be repaired by KEB.
EOL Error Overload Time dependent overload (see overload curves under Technical Data, Section 2.6). Error can not be reset until the display shows E.nOL!	Cause: Excessive motor overload. Factors include: Excessive current. Incorrect motor data. Incorrect encoder configuration. High mechanical load/friction issues. Remedy: Verify correct motor data. Verify correct encoder settings including: LF.27: Encoder Pulse Number LE.28: Swap Encoder Channels (A/B setting) LF.77: Encoder Pole position for PM Synchronous Motors. Check for high mechanical load/issues (friction).
E.OS Error Overspeed The internal overspeed limit is exceeded.	Cause: The inverter internal overspeed is dictated as 125% of the LF.20 Contract Speed. This level is fixed and cannot be adjusted. Possible causes of an overspeed error include: Incorrect setting of the Machine Data parameters LF.20-25: The Machine Data parameters are used as a scalar to convert a linear speed (e.g. ft/min) to a rotary speed (rpm) used by the inverter. If the machine data is not set correctly, the overspeed limit may be calculated too low when control modes which dictate the drive speed exceed this limit. Lack of control: Maximum Torque limit or peak inverter current reached. 0.LF.36 Maximum Torque may be set too low (default = 150%; typical for high speed/full load operation = 200-250%). Excessive current: Incorrect motor data, specifically the motor rated speed and frequency relationship for PM Synchronous Motors, or incorrect Encoder Pole Position (LF.77). Speed gains set too high or low: For an unloaded PM Synchronous Motor, the default speed gains LF.31-33 may be too high, causing the machine to jerk quickly. If left too low for normal operation, the drive may not track the speed. Modulation gain exceeds maximum: If the modulation grade in ru42. exceeds 100%, there may be a loss of speed control. Sudden, excessive movement: Incorrect motor data or incorrect Encoder Pole Position for PM Synchronous Motors. Remedy: Check and verify Machine Data parameters LF.20-25. Monitor the motor current to see if it reaches a current corresponding to the 0.LF.36 Maximum Torque or the drive Peak Current rating. Adjust 0.LF.36 if set too low. Verify motor data, specifically the motor rated speed and frequency relationship for PM Synchronous Motors (see Section 5.6). Verify and correct Encoder Pole Position (LF.77) for PM Synchronous Motors. Relearn Encoder Pole Position as needed (see Section 5.11). Verify speed gains are appropriately configured. Adjust LF.31-33 if needed. Ensure that the modulation grade in ru42. does not exceed 100%.

How to Safely Reset a KEB F5 Fault

Before attempting to clear any fault, you must investigate and resolve the electrical or mechanical issue that triggered the protective shutdown. Once resolved, the drive can be reset using one of the following methods:

1. Keypad Reset: Press the enter or reset key on the drive's attached LCD/LED operator panel to clear the active E.xxx code.
2. Digital Input Reset: If one of the control terminal inputs is mapped to the "Fault Reset" function, apply a momentary 24V transition signal to that terminal to clear the trip.
3. Software Reset: If the drive is connected to a PC, you can trigger a software reset command directly from KEB's COMBIVIS software interface.
4. Power Cycle (Power-On Reset): Turn off the main supply voltage. Important Safety Requirement: Because of the residual energy stored in the internal DC-link capacitors, you must wait at least 5 minutes after switching off the power supply before working on terminals, opening covers, or restoring power.

Most Common KEB F5 Faults and Diagnostic Steps

While the KEB diagnostic system covers many parameters, a few common fault codes represent the majority of typical service calls in industrial settings:

1. E.OC (Error Overcurrent)

The E.OC code triggers if the output current exceeds the drive’s peak current threshold . This can occur during acceleration, deceleration, or steady operation.

• Diagnostic: Check for a mechanical jam in the driven load. Inspect the motor windings and power cabling for insulation degradation or phase-to-ground short circuits. If the fault occurs on start-up even with the motor cables disconnected, the drive’s internal power module (IGBT) may require service.

2. E.OP (Error Overvoltage) & E.UP (Error Undervoltage)

These codes indicate that the voltage on the intermediate DC bus has slipped outside safe operational limits :

• E.OP (Overvoltage): Usually triggers when a high-inertia load decelerates too quickly, acting as a generator and feeding energy back into the drive . Check the dynamic braking resistor for open circuits, or try increasing the deceleration ramp time.
• E.UP (Undervoltage): Indicates that the DC bus voltage has dropped below the minimum operating threshold . Verify the stability of the incoming utility lines and inspect the input contactor or mains fuses.

3. E.EF (Error External Fault) & E.buS (Error Watchdog)

These faults relate to control and external system communication :

• E.EF (External Fault): Triggered when a digital input programmed as an "external fault input" receives a trigger signal . This indicates that an external safety system (such as an emergency stop circuit or motor overtemperature switch) has reported a fault directly to the drive.
• E.buS (Watchdog): Occurs if the drive loses communication with the master PLC or serial communication module for a period longer than the configured watchdog timeout limit . Verify the physical fieldbus cables, connection terminals, and communication parameters.

4. E.br (Error Brake Control)

Specific to applications with mechanical brake control configurations, this error indicates a failure during the brake release or engagement sequence.

• Diagnostic: E.br can trigger if a missing motor phase is detected, if the starting current is too low, or if the current limit is reached during startup before the brake releases . Verify the status of the mechanical brake coil, output contacts, and motor phase balance.

Best Practices to Avoid KEB COMBIVERT F5 Trips

To ensure consistent operation and prolong the life of your KEB F5 drive, consider establishing a proactive preventive maintenance routine:

• Keep Cooling Channels Clean: KEB drives rely on robust heatsink cooling . Dust, lint, or oil mist can block heatsink fans and restrict airflow, leading to premature thermal overtemperature trips (e.g., E.OH or E.OH2) . Periodically clean the cooling channels and check that the fans run smoothly.
• Maintain Environmental Limits: Ensure that the control enclosure is well-ventilated and within the specified temperature limits . Prevent moisture condensation inside the cabinet, as it can damage internal boards .
• Verify Terminal Torque Specs: Undergo regular checks to ensure that power connections (L1, L2, L3, U, V, W) remain tight. Loose terminal screws can cause voltage drops, phase imbalances, and local thermal hotspots.

By understanding what your KEB COMBIVERT F5 drive is reporting through its keypad and performing standard maintenance, you can optimize system uptime and prolong the lifetime of both your inverter and motor.