Causes and corrective actions
Resetting the inverter initializes the internal thermal integrated data of the electronic thermal relay function.
Motor overload trip (electronic thermal relay function)
The electronic thermal relay function in the inverter detects motor overheat due to overload or reduced
cooling capability during constant-speed operation and pre-alarm (TH display) is output when the
integrated value reaches 85% of the Pr. 9 Electronic thermal O/L relay setting and the protection circuit is
activated to stop the inverter output when the integrated value reaches the specified value. When
running a special motor such as a multi-pole motor or multiple motors, provide a thermal relay on the
inverter output side since such motor(s) cannot be protected by the electronic thermal relay function.
1. Check the motor for use under overload.
2. Check that the setting of Pr. 71 Applied motor for motor selection is correct. (Refer to
3. Check that stall prevention operation setting is correct.
1. Reduce the load weight.
2. For a constant-torque motor, set the constant-torque motor in Pr. 71 Applied motor.
3. Check that stall prevention operation setting is correct. (Refer to
If the heatsink overheats, the temperature sensor is actuated to stop the inverter output.
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) in any of Pr. 190 to Pr. 196 (output terminal function selection). (Refer to
1. Check for too high surrounding air temperature.
2. Check for heatsink clogging.
3. Check that the cooling fan is stopped. (Check that
1. Set the surrounding air temperature to within the specifications.
2. Clean the heatsink.
3. Replace the cooling fan.
Instantaneous power failure
If a power failure occurs for longer than 15ms (this also applies to inverter input shut-off), the instantaneous
power failure protective function is activated to trip the inverter in order to prevent the control circuit from
malfunctioning. If a power failure persists for longer than 100ms, the fault 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 15ms.) In some operating status (load magnitude, acceleration/
deceleration time setting, etc.), overcurrent or other protection may be activated upon power restoration.
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
Brake transistor alarm detection/internal circuit fault
This function stops the inverter output if a fault occurs in the brake circuit, e.g. damaged brake
transistors when using functions of the 01800 or more.
In this case, the inverter must be powered off immediately.
For the 01160 or less, it appears when an internal circuit error occurred.
· Reduce the load inertia.
· Check that the frequency of using the brake is proper.
· Check that the brake resistor selected is correct.
For the 01800 or more, when the protective function is activated even if the above measures are taken,
replace the brake unit with a new one.
For the 01160 or less, replace the inverter.
is displayed on the operation panel.)
Inst. Pwr. Loss
Br. Cct. Fault