Having trouble with a KEB COMBIVERT R6 power supply or regen unit? Learn how to troubleshoot E.xxx faults, A.xxx warnings, and status messages like nEtoF and E.LS.

The R6 categorizes its operating status and diagnostics into three distinct displays on the HMI or KEB COMBIVIS programming tool :

• Status Messages (No Prefix): Plain text or abbreviated status codes (e.g., rEGEn, Stb) indicating the current operating condition of the regenerative unit . These do not represent faults and require no action.
• Malfunctions / Alarms (A.xxx): Warnings showing that a parameter has run out of spec, but does not yet threaten the physical components of the unit . The unit continues to run while you investigate.
• Errors / Faults (E.xxx): Critical trip conditions that immediately deactivate modulation (pulse block) . The regeneration circuit will lock down, and you must perform a reset before the unit can resume feeding power back to the grid.

This guide walks you through analyzing KEB R6 error codes, executing a safe reset, and diagnosing common regeneration-specific faults.

KEB COMBIVERT R6 Fault Codes Reference Table

Locate the active E.xxx fault code, A.xxx warning, or status message displaying on your unit to isolate the exact electrical cause of your shutdown.

KEB COMBIVERT R6 Drive Fault Codes List

Status / Fault Code and Meaning	Cause and Solution / Remedy
regen active Status Message	Cause: Normal regeneration operation active. Remedy: Regen active (regeneration operation). No action required; status is informational.
base block Status Message	Cause: Base-block time active. Unit is temporarily blocked from operation. This status precedes all error states. Remedy: Informational status. Wait for the block period to complete automatically.
no operation Status Message	Cause: The enable input is not activated. Output modulation is switched off. Remedy: Activate the enable input to resume operations.
net off Status Message	Cause: Line power failure. Remedy: Regen operation mode is possible; check line supply conditions if unexpected.
standby Status Message	Cause: The unit is enabled but in stand-by operation (motoric operation). Remedy: Informational status; system is ready for operation.
SYn Status Message	Cause: Phase synchronization mode. Remedy: The unit is checking the connection and phase angle of the line voltage.
fault reset level reached Status Message	Cause: Fault reset level reached. Remedy: A fault reset operation is now permitted.
9: ERROR drive overheat Error Message	Cause: Over temperature commutation choke; temperature sensing on the commutation choke indicates the choke is too hot and the overheat delay timer has run out. Remedy: Allow the commutation choke to cool down. Check ventilation and structural choke layout.
31: ERROR External Fault Error Message	Cause: External Fault. The R6 has been programmed to trigger this error for assistance in identifying high regenerative/supply current and line voltage sag (refer to CP.19 settings and section 6.2 for troubleshooting). Remedy: The error can be triggered by an external device through one of the digital inputs, or manually by setting a temporary jumper across X2A.15-X2A.17. Refer to CP.21 - CP.28 for use with the fault log.
40: ERROR line frequency Error Message	Cause: Main Line Frequency out of tolerance. Remedy: Verify the stability and frequency parameters of the input supply.
15: ERROR load shunt fault Error Message	Cause: Load-shunt relay has not picked up; occurs for a short time during the switch-on phase. Remedy: The relay will automatically reset immediately. If the error remains, inspect the load-shunt relay.
3: ERROR net Error Message	Cause: Line power failure: one or more phases are missing. Remedy: Verify the line phases, fuses, and connections.
36: no ERROR overheat Error Message	Cause: Over-temperature condition is no longer present. Remedy: The E.OH overheat error can now be reset.
17: no ERROR overload Error Message	Cause: The cooling period after E.OL is over. Remedy: The overload error can now be reset.
4: ERROR overcurrent Error Message	Cause: Over current; output current too high or ground fault. Remedy: Check the motor, cables, and power connections for ground faults or short circuits.
8: ERROR overheat pow. mod. Error Message	Cause: Over temperature; overheating of the heat sink. Remedy: Check cooling conditions, heatsink fans, and air filters (see "technical data").
6: ERROR overheat internal Error Message	Cause: R6 Unit interior temperature is too high (interior temperature > 95°C). Remedy: Improve ventilation of the enclosure or cabinet housing the R6 unit.
16: ERROR overload Error Message	Cause: Over Load; the actual load was greater than 105% and the overload timer timed out. Remedy: Reduce the load on the motor and drive.
1: ERROR: over voltage Error Message	Cause: Over Voltage; DC bus voltage is too high (> 900VDC). Remedy: Ensure braking resistor or regen unit is properly operating and connected.
49: ERROR pow. unit code inv. Error Message	Cause: Power unit identification is invalid. Remedy: Verify power unit parameters and code compatibility.
50: ERROR pow. unit changed Error Message	Cause: Power unit change detected. Remedy: Refer to parameter CP.31 to acknowledge and verify power unit configuration.
59: synchronization error Error Message	Cause: Synchronization error; connection of line phasing is not correct. Remedy: Check line phasing and connection logic.
2: ERROR under voltage Error Message	Cause: Under voltage; DC bus voltage is too low. Remedy: Verify incoming mains supply voltage levels.
12: ERROR power unit Error Message	Cause: General power circuit error. Remedy: Inspect power unit power stage and connections.
E.Syn Synchronization error	Cause: Line frequency calculated incorrectly. Remedy: If the value in CP.02 is negative, swap L1.1 and L2.1 at the commutation choke so that CP.02 is positive.
E.nEt Error net	Cause: Mains connection or line loss issue. Common factors: Loss of a line phase. High electrical Noise/EMI. Remedy: Refer to Sections 4.4.2 to determine the corresponding wiring of the regen unit (Wiring Scheme A). Verify three-phase supply. Refer to Noise/EMI in Section 6.2.2.
E.OC Error overcurrent	Cause: Elevated output current levels. Common sources: Ground fault or short. High electrical Noise/EMI. Supply or regenerative current too high. Remedy: Check for any loose or missing power connections. Check for similar errors on the (F5) Elevator Drive indicating a ground fault, short, or excessive current. This may indicate the cause of the fault is occurring from the end of the drive, motor contactor, or motor. Refer to Noise/EMI in Section 6.2.2. Check to see if the utilization in CP.6 is high. Refer to High Regenerative/Supply Current in Section 6.2.2. Verify sizing with controller manufacturer.
E.FnEt Error line frequency	Cause: Main line frequency variations. Line frequency out of range (57-60Hz, based on 60Hz nominal line). Generator power operation causes voltage frequency swing. High electrical Noise/EMI. Remedy: Monitor Main Line Frequency at CP.2. Output frequency from generator may be too high/low and may change as various other loads come on/offline. Refer to Noise/EMI in Section 6.2.2.
E.PuCH Error power unit changed	Cause: The voltage class of the line supply has changed since last power on and must be confirmed (cycling power will not clear). Remedy: Re-enter the value in CP.31 to clear the fault. The value displayed cannot be changed and is an arbitrary ID number and NOT a voltage setting.
E.OL Error overload	Cause: Supply or regenerative current too high. Remedy: Check to see if the utilization in CP.6 is high. Refer to High Regenerative/Supply Current in Section 6.2.2. Verify sizing with the controller manufacturer.
E.LSF Error DC Bus charge fault	Cause: If the error does not reset itself after power up and the fault remains, the following causes may be applicable: Load-shunt defective. Input voltage wrong or too low. High losses in the supply cable. Remedy: The unit must be serviced. Verify the line supply or transformer output supply and ensure there is no excessive sags or brown-out conditions.
E.PU Error power unit	Cause: Error on the power stage. Remedy: General error on the power stage. Check grounding of the transformer. If the error is always active, the unit must be sent in for evaluation. If intermittent, it may indicate excessive line sag conditions.
E.UP Error undervoltage	Cause: DC bus level is too low. Remedy: Likely indicates poor power quality. Verify line input voltage. Sagging voltage or loss of phase could cause E.UP error. Check all grounding including X0 of transformer.
E.OP Error Overpotential (faults on F5 Elevator Drive)	Cause: Regen unit is unable to regen back to the line; CP.1 status is not in 'regen' status during generating operation. Enable input not present (CP.1 Status = nop). Input logic not set correctly to recognize enable input (i.e. di.00 = PNP vs. NPN). Regen unit in active fault. DC bus fuse(s) open. Remedy: Verify enable input at X2A.12. When active under normal operation, the CP.1 status should be either 'Stby' or 'rEgEn'. Verify di.00 setting according to input type (PNP: inputs must be +24VDC to be active; NPN: inputs must be at 0VDC to be active). CP.1 status displays fault message or if the fault message has been cleared from the screen by pressing ENTER on the operator keypad, a flashing red indicator LED on the keypad and R6 indicates an active fault remains. Reset (2AX.13) or resolve the cause of the fault. If the fault has been automatically reset, the last fault can be viewed in the fault log, CP.21. If it is unclear whether a fault actually occurred, refer to the note under CP.21...28 to force a specific fault in order to determine if a new fault is occurring. The DC bus fuse(s), internal to the R6, can be checked visibly whether they are open and replaced as needed. Before checking, ensure all safety measures necessary including powering down the unit from the mains disconnect and locking it out and allowing the DC bus to fully dissipate and verifying 0VDC across the DC bus terminals ++, - -.
E.EF External Fault	Cause: Triggered by external device or use of jumper at X2A.15-X2A.17. High regenerative / supply current or excessive line voltage sag causing the DC bus voltage to drop below the level set in CP.19. Remedy: Refer to section 6.2.2 regarding high regenerative / supply current and excessive line voltage sag.
CP.0 Password input	Cause: Restricts parameter editing to authorized personnel. Remedy: Enter password to unlock level access.
CP.1 Status display	Cause: Diagnostics feedback stage. Remedy: Read current operating status or active fault states.
CP.2 Main Line Frequency	Cause: Measures main line frequency of incoming AC power. Remedy: Diagnostic only; check for source frequency instability.
CP.3 AC-Phase current L1	Cause: Measures current draw on phase L1. Remedy: Diagnostic only; monitor for phase current imbalances.
CP.4 AC-Phase current L2	Cause: Measures current draw on phase L2. Remedy: Diagnostic only; monitor for phase current imbalances.
CP.5 AC-Phase current L3	Cause: Measures current draw on phase L3. Remedy: Diagnostic only; monitor for phase current imbalances.
CP.6 Actual Load	Cause: Real-time calculated load on the drive system. Remedy: Diagnostic parameter; check if load regularly exceeds 100%.
CP.7 Actual Load / peak value	Cause: Peak load captured during the current run cycle. Remedy: If peak utilization equals or exceeds 160%, evaluate sizing parameters.
CP.8 DC output current	Cause: Direct current output reading. Remedy: Diagnostic only.
CP.9 Actual DC voltage	Cause: Real-time DC bus voltage level. Remedy: Check if this falls below undervoltage limits or spikes above overvoltage thresholds.
CP.10 DC voltage / peak value	Cause: Highest recorded DC bus voltage level during run. Remedy: Useful for diagnosing overvoltage spike events.
CP.11 Heat sink temperature	Cause: Real-time heatsink temperature monitoring. Remedy: Temperatures should typically remain below 65°C under normal load.
CP.12 Over load counter	Cause: Tracks time-integrated thermal overload status. Remedy: Let the drive stand idle or cool until this returns to 0% to reset E.OL.
CP.13 Active power	Cause: Active power measurement output. Remedy: Diagnostic only.
CP.17 Apparent power / Line input	Cause: Apparent power draw measured from mains input. Remedy: Diagnostic only.
CP.18 Analog output 1 / amplification factor	Cause: Configures analog output scaling. Remedy: Adjust scaling factor to match external monitoring devices.
CP.19 DC bus switching level	Cause: Configurable threshold level for DC bus switching. Remedy: Refer to manual application notes before modifying.
CP.20 Auto error reset counter	Cause: Limits number of consecutive automatic fault resets. Remedy: Adjust value to control automatic retry attempts.
CP.21 Last Error	Cause: Registers the most recently occurred fault code. Remedy: Check value during diagnostics.
CP.22 Last Error 1	Cause: Registers historical fault code (1 fault ago). Remedy: Check value during diagnostics.
CP.23 Last Error 2	Cause: Registers historical fault code (2 faults ago). Remedy: Check value during diagnostics.
CP.24 Last Error 3	Cause: Registers historical fault code (3 faults ago). Remedy: Check value during diagnostics.
CP.25 Last Error 4	Cause: Registers historical fault code (4 faults ago). Remedy: Check value during diagnostics.
CP.26 Last Error 5	Cause: Registers historical fault code (5 faults ago). Remedy: Check value during diagnostics.
CP.27 Last Error 6	Cause: Registers historical fault code (6 faults ago). Remedy: Check value during diagnostics.
CP.28 Last Error 7	Cause: Registers historical fault code (7 faults ago). Remedy: Check value during diagnostics.
CP.29 Software version	Cause: Control unit firmware version identification. Remedy: Useful for firmware compatibility audits.
CP.30 Software date code	Cause: Compilation date of the loaded firmware. Remedy: Informational only.
CP.31 Power part ID code	Cause: Configures or matches power stage hardware voltage class. Remedy: Re-enter correct ID parameter to clear E.PuCH faults after card replacement.
CP.32 Pulse off level	Cause: Modulation shutdown voltage threshold configuration. Remedy: Set according to local grid and application requirements.
CP.33 Operating mode	Cause: Determines control scheme operating mode. Remedy: Select appropriate open/closed loop control profile.
CP.34 Input Type	Cause: Input hardware selection (e.g. PNP vs. NPN). Remedy: Configure to match external sensor wiring logic.
CP.35 Kp Harmonic Filter	Cause: Proportional gain coefficient for the active harmonic filter. Remedy: Tuning parameter; adjust to mitigate line resonance.
CP.36 Ki Harmonic Filter	Cause: Integral gain coefficient for the active harmonic filter. Remedy: Tuning parameter; adjust to stabilize grid synchronization.

2. Replacing the DC Bus Fuses

Step and Objective	Procedural Instructions
Discharge Safety Warning Prerequisite Instruction	Cause: DC Bus capacitors store lethal electrical potential even after mains are isolated. Remedy: ENSURE MAIN POWER HAS BEEN REMOVED AND SUFFICIENT TIME (AT LEAST 5 MINUTES) HAS BEEN ALLOWED FOR THE R6 DC BUS CAPACITORS TO DISCHARGE BEFORE SERVICING. If possible, use a grounding strap to prevent ESD damage to sensitive electronic control components.
Step 1 Remove the Top Cover	Cause: Internal components and fuse block are covered by protective plastic casing. Remedy: Remove the keypad, X2D plug, and X2A terminal strips. Unfasten the cover screws and grounding bar screws, then pull the top cover off.
Step 2 Verify Fuse Condition	Cause: Blown or open DC bus fuses block energy exchange and must be physically identified. Remedy: Inspect the fuses visually. Each fuse has an indicator tab that flips outward if the fuse has opened/blown, indicating replacement is required. Contrast intact fuses with popped-tab open fuses before replacing.
Step 3 Remove the Control Card	Cause: The control card obstructs the physical path needed to extract the fuse blocks safely. Remedy: Unfasten the control card mounting screw and carefully pull the control card assembly straight out.
Step 4 Unplug the Housing Fan	Cause: The housing fan wiring remains coupled to the power stage and prevents complete shell removal. Remedy: Gently unplug the red and black wire lead that connects the housing fan to the power stage board.
Step 5 Remove the Housing	Cause: Outer plastic shell blocks access to the bus bars and hex bolts. Remedy: Unfasten the screw that secures the grounding bracket to the heat sink, then pull the housing off the heatsink. If stuck, use a flat-head screwdriver to gently pry the housing free from the plastic mounting tabs.
Step 6 Replace the Fuses	Cause: Defective fuses must be unbolted and swapped. Remedy: Remove the fuses by unfastening the four M8 hex bolts and washers securing the fuses to the DC bus bars. Install the identical replacement fuses (e.g. Bussmann 170M series) and refasten the four M8 hex bolts and washers. Ensure all four bolts are snug.
Step 7 Re-assemble the R6	Cause: Restoring the drive to fully sealed operational state. Remedy: Reinstall the housing, control card, X2A terminal strips, X2D plug, and keypad in the exact reverse order of disassembly. Note: Be extremely careful when reinstalling the control card; ensure the card's pins are properly aligned before pushing the card into the power stage connector.

3. Document & KEB Contacts Metadata

Contact / Document Field	Reference Information
KEB Germany Headquarters Global HQ Address	Cause: Technical escalating query or factory repairs. Remedy: KEB Automation KG. Försterweg 36-38, D-32683 Barntrup. Tel: +49 5263 401-0. Web: www.keb.de | Email: info@keb.de
KEB America, Inc. North American HQ	Cause: US-based regional support. Remedy: 5100 Valley Industrial Blvd. South, Shakopee, MN 55379. Tel: +1 952 224-1400. Web: www.kebamerica.com | Email: info@kebamerica.com
Document Identifier Archival Metadata	Cause: Maintaining schematic and document version tracking. Remedy: Document ID: 20146460 Part/Version: USA 01 Publication Date: 2018/9
High regenerative or supply current Operational Problem	Cause: Elevated supply or regenerative current. Specific factors include: High nominal motor current. High peak motor current during acceleration/deceleration. Low input voltage / Excessive line sag (a decrease in input voltage causes a corresponding increase in supply current). Overutilization of the regen unit (CP.7 = 160%). Remedy: Check the nominal and peak currents on the F5 Elevator Drive. Determine the causes of high current levels and troubleshoot accordingly. Potentially adjust acceleration/deceleration rates if peak currents are too high. Monitor CP.9 to see if the DC bus voltage is dropping below the CP.19 value during operation. Then, verify and ensure that the incoming line voltage is not sagging during operation. Check CP.6 and CP.7. If CP.7=160%, the regen unit is being overutilized.
Noise/EMI causing intermittent faults Operational Problem (Error overcurrent, Error net, Error line frequency)	Cause: Electrical interference or power supply imbalance. Common factors: Line supply or grounding imbalance. Improperly routed or unshielded DC/AC wiring. Remedy: Line Supply & Grounding: The line supply or transformer secondary MUST be a balanced, center-grounded wye connection. Check for actual physical connection of center-ground. Measure phase-to-ground and phase-to-phase voltages at the R6 unit to ensure they are balanced. EMI Mitigation: Add an additional R6 ferrite ring to the DC bus connections. Installing the incorrect type of ferrite ring will not have an effect on mitigating noise. Verify correct grounding connections, grounding techniques, and panel wire layout. Check for any loose or missing ground connections. Ground conductors must be minimum #4 AWG or a thick ground strap. Ensure DC bus wires (++, - -) are tied together. Any DC, AC, motor leads, or switching power wires (e.g. brake or contactor coil) must be physically separated from each other and not run together. Add additional ferrite ring(s) around all motor lead connections at the drive output (adding individual ferrites around individual motor leads is not necessary).
A.1 Data Logging Setup Appendix: Keypad Setup Menu	Cause: The KEB LCD regen keypad contains built-in capabilities to trending up to 10 parameters or capturing up to 4 fast-scanning parameters triggered by a fault. Remedy: The logging function can be activated from the "Data Logging" menu under the Main Menu of the keypad. An SD card (up to 8GB) is required. Ensure date and time are set on the keypad for accurate timestamps. Generic Parameters: Select up to 10 parameters. General Logging: Enables/disables general data trending. Takes a data point every cycle (.5s fixed sample time × Time Multiplier). Fault Parameters: Select up to 4 parameters. Fault Logging: Enables/disables fast-scanning fault logging. Activated automatically when a fault is triggered in the regen unit.
Base Block Checking (BBL) Appendix: Keypad Parameters	Cause: Base Block (BBL) is a message in the regen unit indicating that the IGBTs have been locked for safety reasons (occurs whenever the unit is disabled or prior to a fault). Remedy: "On": BBL will trigger an event, and a fault file will be created. "Off": BBL is ignored and will not trigger an event. (It is recommended to set this parameter to "Off" for most applications to prevent generating log files at the end of every run).
Datalogging Time & Trigger Adjustments Appendix: Keypad Parameters	Cause: Customizing sample frequency, trigger margins, and pre-trigger inputs for fault diagnostics. Remedy: Sample Time: Base sample time for Fault Logging (Default is 1000 us). Trigger Value: Percentage of time displayed before the event occurred (e.g. if set to 40%, then 40% of the data is displayed before the event, and 60% after). Default is 50%. Time Multiplier: Multiplier of the base sample time for General Logging. Default is 2. Pre-Trigger Source: Allows the event for Fault Logging to be triggered by a digital input instead of a fault. Default is 0. Input 1 (terminal X2A 13) - '16' Input 2 (terminal X2A 13) - '32' Input 3 (terminal X2A 13) - '64' Input 4 (terminal X2A 13) - '128' Input A (internal) - '256' Input B (internal) - '512' Input C (internal) - '1024' Input D (internal) - '2048' Last Fault Code: Displays the decimal code of the last fault.
Recording & Warning Messages Appendix: Keypad Warnings	Cause: SD card active monitoring or file-system warnings. Remedy: The keypad is ready to record when General and/or Fault logging is enabled and an SD card is present. It does not matter which screen the keypad is left on; you can return to CP mode for real-time monitoring. A 2 GB card provides approximately 2 weeks of storage. Warning Messages: "SD card in use do not remove or turn off power" or "Fault Logging in process...": The message will clear if any user action is taken or another system message displays. An icon in the lower right corner indicates the card is in use. "Memory Full, Insert SD card or remove files": The card is full; remove files or replace the card.
Retrieving Logging Data Appendix: Data Management	Cause: Ensuring no log file corruption when ejecting the storage media. Remedy: Once data has been collected, the user must wait one hour before removing the SD card or powering down the unit. This allows all temporary buffer files to be properly written to the SD card. Removing the card early will result in lost data. Remember to turn off logging functions before removal.
Analyzing Logged Data Appendix: Diagnostics Tools	Cause: Interpreting raw parameters and log formats. Remedy: General Logging files are stored as .txt files (convertible to .CSV for Excel viewing). Fault Logging files are stored as .XML files (scope traces viewable in Combivis 6). Common Parameters for Logging: Log the corresponding background parameters (CP parameters cannot be directly logged): ru00: Inverter State ru03: Actual Line Frequency ru08: AC Current L1 ru09: AC Current L2 ru10: AC Current L3 ru11: Input Voltage ru15: DC Current ru17: AC Current ru19: DC Bus Voltage
Using UPS with R6 in Wiring Scheme A Appendix: UPS Wiring Application Note	Cause: Disabling the regen capability of the R6 unit during UPS (Uninterrupted Power Supply) operation to prevent modulating/regenerating back to the UPS, which can cause potential damage to the unit. Remedy: Open the R6 enable (X2A.12) using a relay contact when the UPS is activated. Open/activate an external fault (X2A.15) with another relay contact to further prevent modulation. This keeps the R6 unit in a passive state (input rectifier), allowing it to supply power to the F5 unit to continue driving the motor without regenerating back. Dissipate any excess DC bus voltage through a permanently wired braking resistor on the F5 unit. Under normal operation, no contactor is needed to deactivate the braking resistor because the regen unit modulates at 103% of the nominal idle DC bus voltage (~334VDC for 230V, ~668VDC for 460V), whereas the braking transistor turns on at a much higher level (~380VDC for 230V, ~760VDC for 460V).
Certification Standards Appendix: CE, UL & CSA Marks	Cause: Compliance verification with international safety directives. Remedy: CE Marking: Units comply with Low-Voltage Directive 2006/95/EC, Machinery Directive 2006/42/EC, and EMC Directive 2004/108/EC. Standards applied: EN 61800-5-1, EN 60439-1, EN 60146, and IEC 61800-3. UL Marking: Investigated according to United States Standard UL508C, Third Edition (Power Conversion Equipment) and Canadian Standard CSA C22.2 No.14-2010. CSA Marking: Investigated according to Canadian Standard CSA C22.2 No.14-2010, 11th Edition (Industrial Control Equipment).

How to Safely Reset a KEB R6 Fault

Before initiating a reset, ensure that the underlying issue is resolved. Repeatedly resetting a line or pre-charging fault can damage the unit’s power electronic components.

1. Manual Keypad Reset: Press the enter or reset keys directly on the attached operator interface .
2. Digital Input Reset: If one of the physical digital inputs (ST, I1 to I3) is mapped for fault reset, apply a transition pulse to trigger the reset command.
3. Mains Disconnection (Power Cycle): Shut off the main incoming three-phase AC power lines . Safety Requirement: High residual DC bus voltage remains stored in the capacitors . You must wait a minimum of 5 to 10 minutes (depending on the size of the shared DC bus interconnection) to allow capacitor voltages to discharge below dangerous levels before handling wiring or restoring power.
4. COMBIVIS Reset: Send a remote reset command via the KEB COMBIVIS PC software tool.

Most Common R6 Faults and Troubleshooting Steps

Because the COMBIVERT R6 manages power supply and regeneration, its fault profiles are highly specific compared to typical motor drive controllers:

1. E.LSF (Error Load Shunt Fault)

This is a critical, unit-specific fault indicating that the pre-charging load-shunt relay (or bypass contactor) failed to pick up and close during the initial power-on sequence.

• Diagnostic: Pre-charging resistors are designed to limit high inrush currents when AC power is first applied. If the bypass relay does not close, these resistors will overheat. Check if the incoming three-phase voltage is too low, or if the internal pre-charging relays are physically stuck or damaged.

2. E.nEt (Mains Failure Error) / nEtoF Status

The R6 relies on a synchronized, stable main AC utility connection to safely feed energy back to the grid.

• Diagnostic: nEtoF is a status message indicating that the main grid has experienced a power failure . If the power failure duration exceeds the programmed limit, the unit trips on the hard fault E.nEt . Verify the stability of your incoming power lines, and inspect the main supply fuses and input contactors.

3. E.buS (Error Watchdog)

This error is triggered when serial communication between the operating software, master PLC, or the attached operator and the unit control board is interrupted.

• Diagnostic: Verify that the communication cables are routed away from high-noise power cables. Check the physical RS232/HSP5 adapters and verify that the baud rate and monitoring timeouts are configured correctly.

4. E.OC (Error Overcurrent) & E.OP (Error Overvoltage)

These electrical faults indicate that the current or intermediate DC bus voltage has peaked beyond safe inverter limits.

• Diagnostic: Overcurrent (E.OC) is often triggered by sudden, massive regeneration spikes or ground faults in the DC bus cabling . Overvoltage (E.OP) occurs if the utility grid is unable to accept the recovered energy quickly enough, raising the intermediate bus voltage. Check the sizing of your commutation choke (line choke) and HF filter, and inspect the DC link fuses.

Best Practices for Maintaining the COMBIVERT R6

Because the line regeneration process generates heat and high-frequency electrical harmonics, keeping the following maintenance practices in mind is helpful:

• Verify the Commutation Choke and HF Filter: The R6 requires a properly dimensioned commutation choke and HF filter for EMC compliance and circuit stability . Ensure these accessories are clean and well-connected to prevent harmonics from triggering false overvoltage or line synchronization faults.
• Periodically Check DC Bus Fuses: Due to the high potential currents in shared DC bus layouts, appropriately sized DC fuses are critical to protect against short circuits . Inspect these fuses periodically to ensure they have not suffered from heat stress or fatigue.
• Ensure Adequate Heat Dissipation: Regeneration units generate significant heat when converting kinetic energy . Regularly clean the cooling fan channels and verify the heatsink temperature on the diagnostic menu to avoid thermal overtemperature shutdowns.

By understanding what the KEB COMBIVERT R6 is communicating through its prefix-based display and taking a systematic approach to troubleshooting, you can keep your power regeneration systems running reliably.