Resetting the inverter initializes the internal cumulative heat value of the electronic thermal O/L relay function.
10 ms for IP55 compatible models
6. PROTECTIVE FUNCTIONS
6.5 Causes and corrective actions
Inverter overload trip (Electronic thermal O/L relay)
The electronic thermal O/L relay function in the inverter detects motor overheat, which is caused by overload or
reduced cooling capability during low-speed operation. When the cumulative heat value reaches 85% of the Pr.9
Electronic thermal O/L relay setting, pre-alarm (TH) is output. When the accumulated value reaches the
specified value, the protection circuit is activated to stop the inverter output. When the inverter is used to drive a
dedicated motor, such as a multiple-pole motor, or several motors, the motor cannot be protected by the
electronic thermal O/L relay. Install an external thermal relay on the inverter output side.
• Check the motor for the use under overload.
• Check that the setting of Pr.71 Applied motor for motor selection is correct. (Refer to
• Check that the stall prevention operation setting is correct.
• Reduce the load.
• For a constant-torque motor, set the constant-torque motor in Pr.71.
• Set the stall prevention operation level accordingly. (Refer to
When the heatsink overheats, the temperature sensor is activated, and the inverter output is stopped.
The FIN signal can be output when the temperature becomes approximately 85% of the heatsink overheat
protection operation temperature.
For the terminal used for the FIN signal output, assign the function by setting "26 (positive logic) or 126 (negative
logic)" from Pr.190 to Pr.196 (output terminal function selection). (Refer to
• Check for too high surrounding air temperature.
• Check for heatsink clogging.
• Check that the cooling fan is not stopped. (Check that FN is not displayed on the operation panel.)
• Set the surrounding air temperature to within the specifications.
• Clean the heatsink.
• Replace the cooling fan.
Instantaneous power failure (Standard models and IP55 compatible models only)
If a power failure occurs (or when power input to the inverter is shut off) for longer than 15 ms
instantaneous power failure protective function is activated to shut off the inverter output in order to prevent the
control circuit from malfunctioning. If a power failure persists for 100 ms or longer, the fault warning output is not
provided, and the inverter restarts if the start signal is ON upon power restoration. (The inverter continues
operating if an instantaneous power failure is within 15 ms
acceleration/deceleration time setting, etc.), overcurrent or other protection may be activated upon power
When instantaneous power failure protection is activated, the IPF signal is output. (Refer to
Find the cause of instantaneous power failure occurrence.
• Remedy the instantaneous power failure.
• Prepare a backup power supply for instantaneous power failure.
• Set the function of automatic restart after instantaneous power failure (Pr.57). (Refer to
Undervoltage (Standard models and IP55 compatible models only)
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 to about 150 VAC (300 VAC for the 400 V class) or below, this function shuts off the
When a jumper is not connected across P/+ and P1, the undervoltage protective function is activated.
When undervoltage protection is activated, the IPF signal is output. (Refer to
• Check if a high-capacity motor is driven.
• Check if the jumper is connected across terminals P/+ and P1.
• Check the devices on the power supply line such as the power supply itself.
• Do not remove the jumper across terminals P/+ and P1 except when connecting a DC reactor.
• If the problem still persists after taking the above measure, contact your sales representative.
FR-LU08 indication Motor Ovrload
FR-LU08 indication H/Sink O/Temp
FR-LU08 indication Instantaneous power failure
.) In some operating status (load magnitude,
FR-LU08 indication Under Voltage