Output side earth (ground) fault overcurrent
The inverter output is shut off if an earth (ground) fault overcurrent flows due to an earth (ground) fault that
occurred on the inverter's output side (load side).
Check for a ground fault in the motor and connection cable.
Remedy the earth (ground) fault portion.
Output phase loss
The inverter output is shut off if one of the three phases (U, V, W) on the inverter's output side (load side) is lost.
• Check the wiring. (Check that the motor is normally operating.)
• Check that the capacity of the motor used is not smaller than that of the inverter.
• Check if a start command is given to the inverter while the motor is coasting. (PM motor control)
• Wire the cables properly.
• Input a start command after the motor stops. Alternatively, use the automatic restart after instantaneous power
failure/flying start function
External thermal relay operation
The inverter output is shut off if the external thermal relay provided for motor overheat protection or the internally
mounted thermal relay in the motor, etc. switches ON (contacts open). This function is available when "7" (OH
signal) is set in any of Pr.178 to Pr.189 (Input terminal function selection). This protective function is not
available in the initial status. (OH signal is not assigned.)
• Check for motor overheating.
• Check that the value "7" (OH signal) is set correctly to any of Pr.178 to Pr.189 (Input terminal function
• Reduce the load and operation duty.
• Even if the relay contacts are reset automatically, the inverter will not restart unless it is reset.
PTC thermistor operation
The inverter output is shut off if resistance of the PTC thermistor connected between terminal 2 and terminal 10
is equal to or higher than the Pr.561 PTC thermistor protection level setting for a continuous time equal to or
longer than the setting value in Pr.1016 PTC thermistor protection detection time. When the initial value
(Pr.561 = "9999") is set, this protective function is not available.
• Check the connection with the PTC thermistor.
• Check the Pr.561 and Pr.1016 settings.
• Check the motor for operation under overload.
Reduce the load.
• Appears when the AC power supply is connected to terminal R/L1, S/L2, or T/L3 accidentally when a high
power factor converter (FR-HC2) or power regeneration common converter (FR-CV) is connected (when Pr.30
Regenerative function selection = "2").
• Appears when the switch for manufacturer setting of the plug-in option is changed.
• Appears when a communication option is connected while Pr.296 Password lock level = "0 or 100".
• Check that the AC power supply is not connected to terminal R/L1, S/L2, or T/L3 when a high power factor
converter (FR-HC2) or power regeneration common converter (FR-CV) is connected (when Pr.30 = "2").
• Check for the password lock with a setting of Pr.296 = "0, 100".
• Check the Pr.30 setting and connection with the FR-HC2 or FR-CV.
• The inverter may be damaged if the AC power supply is connected to terminal R/L1, S/L2, or T/L3 when a high
power factor converter is connected. Contact your sales representative.
• Set the switch on the plug-in option, which is for manufacturer setting, back to the initial setting. (Refer to the
Instruction Manual of each option.)
• To apply the password lock when installing a communication option, set Pr.296 ≠ "0, 100". (Refer to
451). (PM motor control)
FR-LU08 indication Ground Fault
FR-LU08 indication Output phase loss
FR-LU08 indication Ext TH relay oper
FR-LU08 indication PTC thermistor oper
FR-LU08 indication Option Fault
6. PROTECTIVE FUNCTIONS
6.5 Causes and corrective actions