Unidrive M100 Drive Fault Codes (2026)

Unidrive M100 Drive Fault Codes (2026) – Troubleshooting guide for Nidec Control Techniques Unidrive M100. Learn to interpret mnemonic trip codes like OI.AC, It.AC, and UV, and use Connect software for diagnostics.

The Nidec Control Techniques Unidrive M100 is an economical, easy-to-use AC drive designed for simple open-loop industrial applications. Despite its entry-level positioning, the M100 features robust protection circuits to safeguard the motor and hardware. When an error occurs, the drive stops the motor and displays a mnemonic trip code—an abbreviated English string such as OI.AC (Overcurrent) or OV (Overvoltage).

This 2026 guide provides the essential information to help you decode these strings, access the drive’s internal trip history, and resolve issues to minimize production downtime.

Unidrive M100 Fault Codes Reference Table

Below is the complete reference list of trips and warnings for the Unidrive M100. Please match the code appearing on your drive’s integrated LED display with the details below.

Fault Code and Meaning

Cause and Remedy

C.Acc (185)

NV Media Card Write fail

Cause: The drive was unable to access the NV Media Card. If the trip occurs during data transfer to the card, the file may be corrupted. If transferring to the drive, data may be incomplete.

Remedy:

Check NV Media Card is installed / located correctly.

Replace the NV Media Card.

C.cPr (188)

NV Media Card file/data is different to the one in the drive

Cause: A compare has been carried out between a file on the NV Media Card and the drive; parameters are different.

Remedy:

Set Pr 00 to 0 and reset the trip.

Check to ensure the correct data block on the NV Media Card has been used for the compare.

C.d.E (179)

NV Media Card data location already contains data

Cause: An attempt has been made to store data on a NV Media Card in a data block which already contains data.

Remedy:

Erase the data in data location.

Write data to an alternative data location.

C.dAt (183)

NV Media Card data not found

Cause: An attempt has been made to access a non-existent file on the NV Media Card. No data is transferred.

Remedy:

Ensure data file number is correct.

C.Err (182)

NV Media Card data structure error

Cause: An error has been detected in the data structure on the card.

Sub-trip	Reason
1	Required folder/file structure not present
2	The 000.DAT file is corrupted
3	Two or more files in folder have same ID

Remedy:

Erase all the data block and re-attempt the process.

Ensure the card is located correctly.

Replace the NV Media Card.

C.FuL (184)

NV Media Card full

Cause: An attempt has been made to create a data block on a NV Media Card, but there is not enough space left on the card.

Remedy:

Delete a data block or the entire NV Media Card to create space.

Use a different NV Media Card.

C.Pr (175)

NV Media Card data blocks are not compatible with the drive derivative

Cause: Drive Derivative (11.028) or Product Type (11.063) are different between the source and target drives.

Sub-trip	Reason
1	Drive Derivative (11.028) is different.
2	Product Type (11.063) is different.

Remedy:

Use a different NV Media Card.

This trip can be suppressed by setting Pr 00 to 9666 and resetting the drive.

Choose a file compatible between the source and target drives (if sub-trip 2).

C.rdo (181)

NV Media Card has the Read Only bit set

Cause: An attempt has been made to modify data on a read-only NV Media Card or read-only data block.

Remedy:

Clear the read only flag by setting Pr 00 to 9777 and reset the drive.

C.rtg (186)

NV Media Card Trip; Voltage/current rating mismatch

Cause: Parameter data is being transferred but the current and/or voltage ratings are different between source and destination drives.

Remedy:

Reset the drive to clear the trip.

Ensure that the drive rating dependent parameters have transferred correctly.

This trip can be suppressed by setting Pr mm.000 to 9666 and resetting the drive.

C.tyP (187)

NV Media Card parameter set not compatible with current drive mode

Cause: Drive mode in the data block is different from the current drive mode, or operating mode is outside allowed range.

Remedy:

Ensure the destination drive supports the drive operating mode in the parameter file.

Clear the value in Pr 00 and reset the drive.

Ensure destination drive operating mode is the same as the source parameter file.

cL.A1 (28)

Analog input 1 current loss

Cause: A current loss was detected in current mode on Analog input 1 (Terminal 2). Current fell below 3 mA (in 4-20 mA or 20-4 mA modes).

Remedy:

Check control wiring is correct.

Check control wiring is undamaged.

Check the Analog Input 1 Mode (07.007).

Current signal is present and greater than 3 mA.

Cur.c (231)

Current calibration range

Cause: Current calibration range error.

Remedy:

Hardware fault – contact the supplier of the drive.

Cur.O (225)

Current feedback offset error

Cause: The current offset is too large to be trimmed.

Remedy:

Ensure that there is no possibility of current flowing in the output phases of the drive when the drive is not enabled.

Hardware fault – contact the supplier of the drive.

d.Ch (97)

Drive parameters are being changed

Cause: A user action or file system write is active that is changing drive parameters while the drive is commanded to enable.

Remedy:

Ensure the drive is not enabled when defaults are being loaded.

dEr.E (246)

Derivative file error

Cause: Derivative file error with sub-trips.

Sub-trip	Reason
1	Derivative file missing or invalid.
2	Derivative file does not match control board hardware.
3	Derivative file changed for a file with different derivative number.

Remedy:

Contact the supplier of the drive.

dEr.I (248)

Derivative product image error

Cause: Error detected in the derivative product image. Identified by sub-trip (e.g., 1: Divide by zero, 30: CRC incorrect, 80: Image not compatible).

Remedy:

Contact the supplier of the drive.

dESt (199)

Two or more parameters are writing to the same destination parameter

Cause: Destination parameters of two or more functions (Menus 7 and 8) are writing to the same parameter.

Remedy:

Set Pr 00 to ‘dest’ or 12001 and check all visible parameters in all menus for parameter write conflicts.

dr.CF (232)

Drive configuration

Cause: The hardware ID does not match the user software ID.

Remedy:

Hardware fault – contact the supplier of the drive.

EEF (31)

Default parameters have been loaded

Cause:

The EEF trip indicates that default parameters have been loaded. The exact cause can be identified from the sub-trip number (e.g., CRC failure, firmware update, hardware change, or power loss during save).

Remedy:

Default the drive and perform a reset.

Allow sufficient time to perform a save before the supply to the drive is removed.

If the trip persists – return drive to supplier.

Et (6)

External trip initiated

Cause:

An External Trip has occurred. This is initiated when Parameter 10.032 is set to 1.

Remedy:

Check the value of Pr 10.032.

Select ‘dest’ (or enter 12001) in Pr 00 and check for a parameter controlling Pr 10.032.

FAn.F (173)

Fan fail

Cause:

The cooling fan has failed or is obstructed. This trip cannot be reset until 10s after the trip was initiated.

Remedy:

Check that the fan is installed and connected correctly.

Check that the fan is not obstructed.

Contact the supplier of the drive to replace the fan.

Fi.Ch (247)

File changed

Cause:

File configuration has changed.

Remedy:

Power cycle the drive.

FI.In (237)

Firmware Incompatibility

Cause:

The FI.In trip indicates that the user firmware is incompatible with the power firmware.

Remedy:

Contact the supplier of the drive.

HF01

Data processing error: CPU hardware fault

Cause:

A CPU address error has occurred. This trip indicates that the control PCB on the drive has failed.

Remedy:

Hardware fault – Contact the supplier of the drive.

HF02

Data processing error: CPU memory management fault

Cause:

A DMAC address error has occurred. This trip indicates that the control PCB on the drive has failed.

Remedy:

Hardware fault – Contact the supplier of the drive.

HF03

Data processing error: Bus fault

Cause:

The CPU has detected a bus fault. This trip indicates that the control PCB on the drive has failed.

Remedy:

Hardware fault – Contact the supplier of the drive.

HF04

Data processing error: Usage fault

Cause:

The CPU has detected a usage fault. This trip indicates that the control PCB on the drive has failed.

Remedy:

Hardware fault – Contact the supplier of the drive.

HF07

Data processing error: Watchdog failure

Cause:

A watchdog failure has occurred. This trip indicates that the control PCB on the drive has failed.

Remedy:

Hardware fault – Contact the supplier of the drive.

HF08

Data processing error: CPU Interrupt crash

Cause:

A CPU interrupt crash has occurred. The crash level is indicated by the sub-trip number.

Remedy:

Hardware fault – Contact the supplier of the drive.

HF09

Data processing error: Free store overflow

Cause:

A free store overflow has occurred. This trip indicates that the control PCB on the drive has failed.

Remedy:

Hardware fault – Contact the supplier of the drive.

HF11

Data processing error: Non-volatile memory comms error

Cause:

A non-volatile memory comms error has occurred. Sub-trip 1: Comms error. Sub-trip 2: EEPROM size incompatible with firmware.

Remedy:

Hardware fault – Contact the supplier of the drive.

HF12

Data processing error: Main program stack overflow

Cause:

The main program stack overflow has occurred. The stack can be identified by the sub-trip number (Derivative or Main system stacks).

Remedy:

Hardware fault – Contact the supplier of the drive.

HF16

Data processing error: RTOS error

Cause:

An RTOS (Real Time Operating System) error has occurred.

Remedy:

Hardware fault – Contact the supplier of the drive.

HF19

Data processing error: CRC check on firmware failed

Cause:

The CRC check on the drive firmware has failed.

Remedy:

If this trip occurs – contact the supplier of the drive.

HF23

Hardware fault

Cause:

General hardware fault detected.

Remedy:

Hardware fault – Contact the supplier of the drive.

It.Ac (20)

Output current overload timed out (I2t)

Cause:

Motor thermal overload based on Motor Rated Current and Thermal Time Constant. The drive trips when the accumulator (Pr 04.019) reaches 100%.

Remedy:

Ensure the load is not jammed / sticking.

Check the load on the motor has not changed.

Ensure the motor rated current is not zero.

It.br (19)

Braking resistor overload timed out (I2t)

Cause:

Braking resistor overload has timed out. Initiated when Braking Resistor Thermal Accumulator (10.039) reaches 100%.

Remedy:

Ensure the values entered in Pr 10.030, Pr 10.031 and Pr 10.061 are correct.

Check resistor value and power rating.

If an external thermal protection device is used and software protection is not required, disable the trip via parameters.

no.PS (236)

No power board

Cause:

No communication between the power and control boards.

Remedy:

Hardware fault – Contact the supplier of the drive.

O.Ld1 (26)

Digital output overload

Cause:

Total current drawn from the AI Adaptor 24 V or from the digital output has exceeded the limit.

Remedy:

Check total loads on digital outputs and 24 V.

Check control wiring is correct.

Check output wiring is undamaged.

O.SPd (7)

Motor frequency has exceeded threshold

Cause:

In open-loop mode, the Post-ramp Reference exceeds the Over Frequency Threshold in either direction.

Remedy:

Check that a mechanical load is not driving motor.

Reduce Current Controller Ki Gain (04.014).

Oh.dc (27)

DC bus over temperature

Cause:

DC bus component over-temperature based on a software thermal model (Pr 07.035 reaches 100%). Includes effects of output current and DC bus ripple.

Remedy:

Check the AC supply voltage balance and levels.

Check DC bus ripple level.

Reduce duty cycle or motor load.

Check output current stability.

Check motor map settings.

Disable slip compensation or dynamic V to F if necessary.

Oht.C (219)

Control stage over-temperature

Cause:

Control stage over-temperature detected if Cooling Fan control (06.045) = 0.

Remedy:

Increase ventilation by setting Cooling Fan control (06.045) > 0.

Oht.I (21)

Inverter over temperature based on thermal model

Cause:

IGBT junction over-temperature detected based on software thermal model (reaches 145 °C).

Remedy:

Reduce the selected drive switching frequency.

Ensure Auto-switching Frequency Change Disable (05.035) is OFF.

Reduce duty cycle.

Increase acceleration / deceleration rates.

Reduce motor load.

Check DC bus ripple.

Ensure all three input phases are present and balanced.

Oht.P (22)

Power stage over temperature

Cause: A power stage over-temperature has been detected. The Thermistor location is identified by the sub-trip.

Remedy:

Check enclosure / drive fans are still functioning correctly.

Force the heatsink fans to run at maximum speed.

Check enclosure ventilation paths.

Check enclosure door filters.

Increase ventilation.

Reduce the drive switching frequency.

Reduce duty cycle.

Increase acceleration / deceleration rates.

Use S ramp (Pr 02.006).

Reduce motor load.

Check the derating tables and confirm the drive is correctly sized for the application.

Use a drive with larger current / power rating.

OI.A1 (189)

Analog input 1 over-current

Cause: Current input on analog input 1 exceeds 24mA.

Remedy:

Check the signal source connected to Analog Input 1.

Ensure input current is within the specified range (below 24mA).

OI.AC (3)

Instantaneous output over current detected

Cause: The instantaneous drive output current has exceeded VM_DRIVE_CURRENT_MAX. This trip cannot be reset until 10s after the trip was initiated.

Remedy:

Increase acceleration/deceleration rate.

If seen during autotune reduce the voltage boost.

Check for short circuit on the output cabling.

Check integrity of the motor insulation using an insulation tester.

Check if the motor cable length is within limits for the frame size.

Reduce the values in the current loop gain parameters.

OI.br (4)

Braking IGBT over current detected

Cause: Over current has been detected in braking IGBT or braking IGBT protection has been activated. This trip cannot be reset until 10s after the trip was initiated.

Remedy:

Check brake resistor wiring.

Check braking resistor value is greater than or equal to the minimum resistance value.

Check braking resistor insulation.

OI.SC (228)

Output phase short-circuit

Cause: Over-current detected on drive output when enabled. Possible motor ground fault.

Remedy:

Check for short circuit on the output cabling.

Check integrity of the motor insulation using an insulation tester.

Check if the motor cable length is within limits for the frame size.

Out.P (98)

Output phase loss detected

Cause: Phase loss has been detected at the drive output. (Sub-trip 1=U, 2=V, 3=W, 4=Output freq >4Hz and disconnected).

Remedy:

Check motor and drive connections.

To disable the trip set Output Phase Loss Detection Enable (06.059) = 0.

OV (2)

DC bus voltage exceeded peak/continuous level

Cause: DC bus voltage has exceeded the VM_DC_VOLTAGE[MAX] or VM_DC_VOLTAGE_SET[MAX] for 15s.

Remedy:

Increase deceleration ramp (Pr 04).

Decrease the braking resistor value (staying above the minimum value).

Check nominal AC supply level.

Check for supply disturbances which could cause the DC bus to rise.

Check motor insulation using an insulation tester.

P.dAt (220)

Power system configuration data error

Cause: Error in the configuration data stored in the power system. Trip generated from within drive control system or from power system.

Remedy:

Hardware fault – Contact the supplier of the drive.

Pb.bt (245)

Power board is in bootloader mode

Cause: Power board is stuck in bootloader mode.

Remedy:

Contact the supplier of the drive.

Pb.Er (93)

Communication lost / errors between control and power

Cause: No communications between the control board processor and the power board processor.

Remedy:

Hardware fault – Contact the supplier of the drive.

Pb.HF (235)

Power board HF

Cause: Power processor hardware fault. The sub-trip number is the HF code.

Remedy:

Hardware fault – Contact the supplier of the drive.

Pd.S (37)

Power down save error

Cause: An error has been detected in the power down save parameters saved in non-volatile memory.

Remedy:

Perform a 1001 save in Pr 00 to ensure that the trip doesn’t occur the next time the drive is powered up.

PH.Lo (32)

Supply phase loss

Cause: Input phase loss or large supply imbalance detected. DC bus ripple exceeds threshold.

Remedy:

Check the AC supply voltage balance and level at full load.

Check the DC bus ripple level with an isolated oscilloscope.

Check the output current stability.

Check for mechanical resonance with the load.

Reduce the duty cycle.

Reduce the motor load.

Disable the phase loss detection, set Pr 06.047 to 2.

PSU (5)

Internal power supply fault

Cause: One or more internal power supply rails are outside limits or overloaded.

Remedy:

There is a hardware fault within the drive – return the drive to the supplier.

r.b.ht (250)

Hot rectifier/brake

Cause: Over-temperature detected on input rectifier or braking IGBT.

Remedy:

Increase ventilation by setting Cooling Fan Control (06.045) > 0.

Reserved Trips

Various Codes

Cause: These trip numbers are reserved trip numbers for future use.

Remedy:

Trip Numbers: 01, 09, 12, 14-17, 23, 29, 38, 39, 90-96, 99, 101-109, 111, 168-172, 176-177, 190-198, 205-217, 222-224, 229-233, 238-244, 249, 251-254.

rS (33)
Measured resistance has exceeded the parameter range

Cause:

The measured stator resistance of the motor during an autotune test has exceeded the maximum possible value. This often happens if the motor is very small compared to the drive rating.

Sub-trip indications:

0: Stator resistance is greater than full scale limit.

2: Measured Transient Inductance > 500 mH or Stator Inductance > 5000 mH.

3: User entered resistance value is too high.

4: Measured resistance outside firmware usable range.

Remedy:

Ensure the stator resistance of the motor falls within the range of the drive model.

Check that the ratio of drive size to motor size is not greater than 15:1.

Check that a value has not been entered in the stator resistance that exceeds the allowed range.

Check the motor cable / connections.

Check the integrity of the motor stator winding using an insulation tester.

Check the motor phase to phase resistance at the drive terminals and motor terminals.

Select fixed boost mode (Pr 05.014 = Fd) and verify output current waveforms with an oscilloscope.

Replace the motor.

So.St (226)
Soft start relay failed to close, soft start monitor failed

Cause:

The soft start relay in the drive failed to close or the soft start monitoring circuit has failed.

Sub-trip indications:

1: Soft-start failure.

2: DC bus capacitor failure on 110 V drive.

Remedy:

Hardware fault – Contact the supplier of the drive.

St.HF (221)
Hardware trip has occurred during last power down

Cause:

A hardware trip (HF01 – HF18) has occurred and the drive has been power cycled. The sub-trip number identifies the specific HF trip.

Remedy:

Enter 1299 in Pr mm.000 and press reset to clear the trip.

Sto (234)
No Safe Torque Off board fitted

Cause:

Internal STO board not fitted correctly.

Remedy:

Hardware fault – Contact the supplier of the drive.

th.br (10)
Brake resistor over temperature

Cause:

The hardware based braking resistor thermal monitoring is connected and the resistor overheats. If the braking resistor is not used, bit 3 of Action On Trip Detection (10.037) must be disabled.

Remedy:

Check brake resistor wiring.

Check braking resistor value is greater than or equal to the minimum resistance value.

Check braking resistor insulation.

tH.Fb (218)
Internal thermistor has failed

Cause:

An internal thermistor has failed in the drive (i.e. open circuit or short circuit). The sub-trip identifies the specific thermistor location.

Remedy:

Hardware fault – Contact the supplier of the drive.

tun.S (18)
Autotune test stopped before completion

Cause:

The drive was prevented from completing an autotune test because either the drive enable or the drive run signals were removed.

Remedy:

Check the drive enable signal (Terminal 11) was active during the autotune.

Check the run command was active in digital input 3 or 4 state (Pr 08.003 or Pr 08.004) during the autotune.

tun.1 (11)
Required speed could not be reached

Cause:

The drive tripped during an autotune because the motor did not reach the required speed (Sub-trip 2).

Remedy:

Ensure the motor is free to turn (i.e. mechanical brake is released).

U.OI (8)
User OI ac

Cause:

The output current of the drive exceeded the trip level set by User Over Current Trip Level (04.041).

Remedy:

Check the User Over Current Trip Level setting (04.041).

Check the load on the motor.

U.S (36)
User Save error / not completed

Cause:

An error has been detected in the user save parameters saved in non-volatile memory (e.g. power removed while saving).

Remedy:

Perform a user save in Pr 00 to ensure that the trip doesn’t occur the next time the drive is powered up.

Ensure that the drive has enough time to complete the save before removing the power to the drive.

HF01 – HF23
Internal / Hardware trips

Cause:

Internal faults detected by the main drive processor. These are irrecoverable errors.

Remedy:

Power cycle the drive.

If the trip persists (St.HF), the sub-trip number indicates the HF fault code.

Enter 1299 in Pr 00 to clear the Stored HF trip.

br.res
Brake resistor overload

Cause:

Braking Resistor Thermal Accumulator (10.039) in the drive has reached 75.0 % of the value at which the drive will trip.

Remedy:

Check the braking resistor sizing.

Monitor Pr 10.039.

OV.Ld
Motor Protection Accumulator Warning

Cause:

Motor Protection Accumulator (04.019) in the drive has reached 75.0 % of the value at which the drive will trip and the load on the drive is >100 %.

Remedy:

Reduce motor load.

Check motor rated current settings.

d.OV.Ld
Drive over temperature

Cause:

Percentage Of Drive Thermal Trip Level (07.036) in the drive is greater than 90 %.

Remedy:

Check drive cooling and ambient temperature.

Ensure vents are not obstructed.

tuning
Autotune in progress

Cause:

The autotune procedure has been initialized and an autotune is currently in progress.

Remedy:

Wait for autotune to complete.

LS
Limit switch active

Cause:

Indicates that a limit switch is active and that is causing the motor to be stopped.

Remedy:

Check limit switch mechanical position and wiring.

Lo.AC
Low voltage mode

Cause:

Drive is operating in Low voltage mode. See Low AC Alarm (10.107).

Remedy:

Check input voltage supply.

Verify parameter 10.107 settings.

I.AC.Lt
Current limit active

Cause:

The drive current limit is active. See Current Limit Active (10.009).

Remedy:

Check for mechanical load issues.

Verify current limit parameters.

24.LoSt
24V backup not present

Cause:

24V backup supply is missing. See 24V Alarm Loss Enable (11.098).

Remedy:

Check external 24V power supply.

Check wiring to the backup terminals.

inh
Drive inhibited

Cause:

The drive is inhibited and cannot be run. Either the drive enable signal is not applied to the drive enable terminals or Pr 06.015 is set to 0. (Output Stage: Disabled)

Remedy:

Apply Enable signal to terminals.

Set Pr 06.015 to 1.

rdy
Ready to run

Cause:

The drive enable is active, but the drive inverter is not active because the final drive run is not active. (Output Stage: Disabled)

Remedy:

Apply Run command (Start signal).

Stop
Drive stopped

Cause:

The drive is stopped / holding zero speed. (Output Stage: Enabled)

Remedy:

Information only; drive is holding torque at zero speed.

S.Loss
Supply loss

Cause:

Supply loss condition has been detected. (Output Stage: Enabled)

Remedy:

Check incoming AC power supply.

Check input fuses.

dc.inj
DC injection braking

Cause:

The drive is applying DC injection braking. (Output Stage: Enabled)

Remedy:

Wait for braking cycle to finish.

Er
Drive tripped

Cause:

The drive has tripped and no longer controlling the motor. The trip code appears in the display. (Output Stage: Disabled)

Remedy:

Look at the specific trip code on the display and troubleshoot that specific error.

UV
Under voltage

Cause:

The drive is in the under voltage state either in low voltage or high voltage mode. (Output Stage: Disabled)

Remedy:

Check DC bus voltage.

Check AC supply voltage.

HEAt
Motor pre-heat

Cause:

The motor pre-heat function is active. (Output Stage: Enabled)

Remedy:

Information only. Function used to prevent condensation in motor.

PS.LOAD
Waiting for power stage

Cause:

The drive is waiting for the processor in the power stage to respond after power-up.

Remedy:

Normal during startup. If it hangs here, check internal connections or replace drive.

Note: On the M100, a “Warning” will flash on the display while the motor continues to run. A “Trip” will be a solid code that causes the motor to coast or ramp to a stop.

How to Read M100 Faults via Connect Software

In 2026, while the M100 is designed for simplicity, complex intermittent issues may require more than just the front display. To access deeper diagnostics, you can connect the M100 to a PC.

AI-485 Adapter: Since the M100 does not have a built-in serial port, you must use the optional AI-485 adapter (or AI-Backup adapter) to connect the drive to a PC via a CT-USB-Cable.
Connect Software: Using Nidec’s “Connect” software, you can view the Trip Log. This provides a clearer view of the drive’s status at the time of the trip than the 2-digit mnemonic.
Trip History (Menu 10): The M100 stores the last 10 trips in Parameters 10.020 to 10.029. Parameter 10.020 always displays the most recent trip.
Sub-trip Strings: Some trips (like internal hardware faults) have sub-trip strings that provide specific technical data. These are accessible via parameter 10.070 using the software.

Frequently Asked Questions (FAQ)

Q: What is the difference between a Trip and a Warning?

A: A Trip (Solid code) is a protective shutdown that stops the motor to prevent damage. A Warning (Flashing code) notifies you that the drive is reaching a limit—such as O.Ld1 (Load Warning)—but it will keep the motor running for as long as it is safe.

Q: How do I reset a Unidrive M100 trip?

A: Once the cause of the fault is resolved, reset the drive via:

Pressing the Red STOP/RESET button on the keypad.
Cycling the Main Power (Wait for the display to turn off fully before reapplying power).
Toggling a Digital Input assigned to the “Reset” function (typically Terminal 4 if configured).
Sending a reset command via Modbus RTU (requires the AI-485 adapter).

Q: Where is the fault history stored?

A: Fault history is stored in the drive’s non-volatile memory in Menu 10. This log is retained even if the drive is powered down for maintenance.

Q: What does “UV” mean?

A: “UV” stands for Under Voltage. This indicates that the DC bus voltage has dropped below the minimum threshold. This is common during a power outage or if the incoming AC supply sags significantly under load.

Q: What does “ih” mean on the display?

A: “ih” stands for Inhibit. This is a status code, not a fault. It means the drive is healthy but cannot run because the Safe Torque Off (STO) or Enable signal is missing. Check your safety circuit wiring.