Resetting the inverter
The inverter can be reset by performing any of the following operations. Note that the internal thermal integrated value of the electronic thermal relay function and the number of retries are cleared (erased) by resetting the inverter.
Recover about 1s after reset is cancelled.
Operation 1:  Using the operation panel, press to reset the inverter. (This may only be performed when a fault occurs)
Operation 2:  Switch power off once, then switch it on again.
Operation 3: Turn on the reset signal (RES) for more than 0.1s. (If the RES signal is kept on, "Err." appears (flickers) to indicate that the inverter is in a reset status.)

Er3 Calibration error
Description Analog input bias and gain calibration values are too close.
Check point Check the settings of C3, C4, C6 and C7 (calibration functions).
--------------------
Er4 Mode designation error
Description You attempted to make parameter setting in the NET operation mode when Pr. 77 is not 2.
Check point
1. Check that operation mode is PU operation mode.
2. Check the Pr. 77 setting. 
Corrective action
1. After setting the operation mode to the "PU operation mode", make parameter setting.
2. After setting "2" in Pr. 77, make parameter setting.
--------------------
Err. Inverter reset
Description
+ Executing reset using RES signal, or reset command from communication or PU
+ Displays at powering off.
Corrective action + Turn off the reset command
--------------------
OL Stall prevention (overcurrent)
During acceleration
When the output current of the inverter exceeds the stall prevention operation level (Pr. 22 Stall prevention operation level, etc.), this function stops the increase in frequency until the overload current decreases to prevent the inverter from resulting in overcurrent trip. When the overload current has reduced below stall prevention operation level, this function increases the frequency again.
During constantspeed operation
When the output current of the inverter exceeds the stall prevention operation level (Pr. 22 Stall prevention operation level, etc.), this function reduces frequency until the overload current decreases to prevent the inverter from resulting in overcurrent trip. When the overload current has reduced below stall prevention operation level, this function increases the frequency up to the set value.
During deceleration
When the output current of the inverter exceeds the stall prevention operation level (Pr. 22 Stall prevention operation level, etc.), this function stops the decrease in frequency until the overload current decreases to prevent the inverter from resulting in overcurrent trip. When the overload current has decreased below stall prevention operation level, this function decreases the frequency again.
Check point
1. Check that the Pr. 0 Torque boost setting is not too large.
2. Check that the Pr. 7 Acceleration time and Pr. 8 Deceleration time settings are not too small.
3. Check that the load is not too heavy.
4. Are there any failure in peripheral devices?
5. Check that the Pr. 13 Starting frequency is not too large.
6. Check that the Pr. 22 Stall prevention operation level is appropriate
Corrective action
1. Increase or decrease the Pr. 0 Torque boost setting 1% by 1% and check the motor status.
2. Set a larger value in Pr. 7 Acceleration time and Pr. 8 Deceleration time.
3. Reduce the load weight.
4. Try general-purpose magnetic flux vector control.
5. Change the Pr. 14 Load pattern selection setting.
6. Set stall prevention operation current in Pr. 22 Stall prevention operation level. (The initial value is 150%.) The acceleration/deceleration time may change. Increase the stall prevention operation level with Pr. 22 Stall prevention operation level, or disable stall prevention with Pr. 156 Stall prevention operation selection. (Operation at OL occurrence can be selected using Pr. 156.)
During deceleration
+ If the regenerative energy of the motor becomes excessive to exceed the regenerative energy consumption capability, this function stops the decrease in frequency to prevent overvoltage trip.
As soon as the regenerative energy has reduced, deceleration resumes.
+ If the regenerative energy of the motor becomes excessive when regeneration avoidance function is selected (Pr. 882 =1), this function increases the speed to prevent overvoltage trip..
Check point
+ Check for sudden speed reduction.
+ Check that regeneration avoidance function (Pr. 882, Pr. 883, Pr. 885, Pr. 886) is used.
Corrective action The deceleration time may change. Increase the deceleration time using Pr. 8 Deceleration time.
--------------------
PS PU stop
Stop with of the PU is set in Pr. 75 Reset selection/disconnected PU detection/PU stop selection. (For Pr. 75.)

Check point

Check for a stop made by pressing of the operation panel.
Corrective action Turn the start signal off and release with
--------------------
RB Regenerative brake prealarm
Appears if the regenerative brake duty reaches or exceeds 85% of the Pr. 70 Special regenerative brake duty value.
When the setting of Pr. 70 Special regenerative brake duty is the initial value (Pr. 70 = "0"), this warning does not occur. If the regenerative brake duty reaches 100%, a regenerative overvoltage (E. OV_) occurs.
The RBP signal can be simultaneously output with the [RB] display. For the terminal used for the RBP signal output, assign the function by setting "7 (positive logic) or 107 (negative logic)" in Pr. 190 or Pr. 192 (output terminal function selection).

Check point

1. Check that the brake resistor duty is not high.
2. Check that the Pr. 30 Regenerative function selection and Pr. 70 Special regenerative brake duty settings are correct.

Corrective action

1. Increase the deceleration time.
2. Check that the Pr. 30 Regenerative function selection and Pr. 70 Special regenerative brake duty settings.
--------------------
TH Electronic thermal relay function prealarm
Appears if the cumulative value of the Pr. 9 Electronic thermal O/L relay reaches or exceeds 85% of the preset level. If it reaches 100% of the Pr. 9 Electronic thermal O/L relay setting, a motor overload trip (E. THM) occurs.
The THP signal can be simultaneously output with the [TH] display. For the terminal used for THP signal output, assign the function by setting "8 (positive logic) or 108 (negative logic)" in Pr. 190 or Pr. 192 (output terminal function selection).
Check point
1. Check for large load or sudden acceleration.
2. Is the Pr. 9 Electronic thermal O/L relay setting is appropriate?
Corrective action
1. Reduce the load and frequency of operation.
2. Set an appropriate value in Pr. 9 Electronic thermal O/L relay.
--------------------
MT Maintenance signal output
Description
Indicates that the cumulative energization time of the inverter has reached a given time.
When the setting of Pr. 504 Maintenance timer alarm output set time is the initial value (Pr. 504 = "9999"), this warning does not occur.
Check point
The Pr. 503 Maintenance timer setting is larger than the Pr. 504 Maintenance timer alarm output set time setting.
Corrective action Setting "0" in Pr. 503 Maintenance timer erases the signal.
--------------------
UV Undervoltage
Description
If the power supply voltage of the inverter decreases, the control circuit will not perform normal functions. In addition, the motor torque will be insufficient and/or heat generation will increase. To prevent this, if the power supply voltage decreases below about 115VAC (230VAC for 400V class), this function stops the inverter output and displays .
An alarm is reset when the voltage returns to normal.

Check point

Check that the power supply voltage is normal.
Corrective action Check the power supply system equipment such as power supply.
--------------------
FN Fan fault

Description

For the inverter that contains a cooling fan, appears on the operation panel when the cooling fan stops due to an alarm or different operation from the setting of Pr. 244 Cooling fan operation selection.

Check point

Check the cooling fan for an alarm.
Corrective action Check for fan alarm. Please contact your sales representative.
--------------------
E.OC1 OC During Acc
Overcurrent trip during acceleration
Description When the inverter output current reaches or exceeds approximately 200% of the rated current during acceleration, the protective circuit is activated and the inverter trips.
Check point
1. Check for sudden acceleration.
2. Check that the downward acceleration time is not long in vertical lift application.
3. Check for output short-circuit/ground fault.
4. Check that stall prevention operation is appropriate.
5. Check that regeneration is not performed frequently. (Check that the output voltage becomes larger than the V/F reference value at regeneration and overcurrent occurs due to the high voltage.)
Corrective action
1. Increase the acceleration time. (Shorten the downward acceleration time in vertical lift application.
2. When "E.OC1" is always lit at starting, disconnect the motor once and start the inverter.
If "E.OC1" is still lit, contact your sales representative.
3. Check the wiring to make sure that output short circuit/ground fault does not occur.
4. Perform stall prevention operation appropriately.
5. Set base voltage (rated voltage of the motor, etc.) in Pr. 19 Base frequency voltage.
--------------------
E.OC2 Stedy Spd OC
Overcurrent trip during constant speed

Description

When the inverter output current reaches or exceeds approximately 200% of the rated current during constant speed operation, the protective circuit is activated and the inverter trips.
Check point
1. Check for sudden load change.
2. Check for output short-circuit/ground fault.
3. Check that stall prevention operation is appropriate.
Corrective action
1. Keep load stable.
2. Check the wiring to make sure that output short circuit/ground fault does not occur.
3. Perform stall prevention operation appropriately.
--------------------
E.OC3 OC During Dec
Overcurrent trip during deceleration or stop
Description When the inverter output current reaches or exceeds approximately 200% of the rated inverter current during deceleration (other than acceleration or constant speed), the protective circuit is activated and the inverter trips.
Check point
1. Check for sudden speed reduction.
2. Check for output short-circuit/ground fault.
3. Check for too fast operation of the motor's mechanical brake.
4. Check that stall prevention operation is appropriate.
Corrective action
1. Increase the deceleration time.
2. Check the wiring to make sure that output short circuit/ground fault does not occur.
3. Check the mechanical brake operation.
4. Perform stall prevention operation appropriately.
--------------------
E.OV1 OV During Acc
Regenerative overvoltage trip during acceleration
Description
If regenerative energy causes the inverter's internal main circuit DC voltage to reach or exceed the specified value, the protective circuit is activated and the inverter trips. The circuit may also be activated by a surge voltage produced in the power supply system.

Check point

1. Check for too slow acceleration. (e.g. during downward acceleration in vertical lift load)
2. Check that the Pr. 22 Stall prevention operation level is not lower than the no load current.
Corrective action
1. + Decrease the acceleration time.
+ Check that regeneration avoidance function (Pr. 882, Pr. 883, Pr. 885, Pr. 886) is used.
2. Set a value larger than the no load current in Pr. 22 Stall prevention operation level.
--------------------
E.OV2 Stedy Spd OV
Regenerative overvoltage trip during constant speed
Description
If regenerative energy causes the inverter's internal main circuit DC voltage to reach or exceed the specified value, the protective circuit is activated to stop the inverter output. The circuit may also be activated by a surge voltage produced in the power supply system.

Check point

1. Check for sudden load change.
2. Check that the Pr. 22 Stall prevention operation level is not lower than the no load current.
1. + Keep load stable.
+ Check that regeneration avoidance function (Pr. 882, Pr. 883, Pr. 885, Pr. 886) is used.
+ Use the brake resistor, brake unit or power regeneration common converter (FR-CV) as required.
2. Set a value larger than the no load current in Pr. 22 Stall prevention operation level.
--------------------

+ Mitsubishi VFD Fault code page 1 >

+ Mitsubishi VFD Fault code page 2 >

- Mitsubishi Vfd User manual

- Mitsubishi VFD Contact

- VFD Main page 

---------