Causes and corrective actions
Motor overload trip (electronic thermal relay function) ∗1
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.
Check the motor for use under overload.
Check that the setting of Pr. 71 Applied motor for motor selection is correct. (Refer to page 118).
Check that stall prevention operation setting is correct.
Reduce the load weight.
For a constant-torque motor, set the constant-torque motor in Pr. 71 Applied motor.
Check that stall prevention operation setting is correct. (Refer to page 92).
Resetting the inverter initializes the internal thermal integrated data of the electronic thermal relay function.
If the heatsink overheats, the temperature sensor is actuated and the inverter trips.
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. 192 (output terminal function selection). (Refer to page 145).
Check for too high surrounding air temperature.
Check for heatsink clogging.
Check that the cooling fan is not stopped (Check that
Set the surrounding air temperature to within the specifications.
Clean the heatsink.
Replace the cooling fan.
Input phase loss ∗
Inverter trips when function valid setting (=1) is selected in Pr. 872 Input phase loss protection selection and one phase of
the three phase power input is lost. (Refer to page 172).
It may be available if phase-to-phase voltage of the three-phase power input becomes largely unbalanced.
Check for a break in the cable for the three-phase power supply input.
Check that phase-to-phase voltage of the three-phase power input is not largely unbalanced.
Wire the cables properly.
Repair a break portion in the cable.
Check the Pr. 872 Input phase loss protection selection setting.
Set Pr. 872 = "0" (without input phase loss protection) when three-phase input voltage is largely unbalanced.
∗ Available only for three-phase power input model.
Stall prevention stop
If the output frequency has fallen to 1Hz by stall prevention operation and remains for 3s, a fault (E.OLT) appears and
trips the inverter. OL appears while stall prevention is being activated.
E.OLT may not occur if stall prevention (OL) is activated during output phase loss.
Check the motor for use under overload. (Refer to page 93).
Reduce the load weight. (Check the Pr. 22 Stall prevention operation level setting.)
is not displayed on the operation panel).
Input phase loss
Stll Prev STP (OL shown during stall prevention operation)