Mitsubishi Electric FR-A820-00046 Instruction Manual page 912

Causes and corrective actions
Operation panel
indication
Name
Description
Check point
Corrective action
Operation panel
indication
Name
Description
Check point
Corrective action
6 - 24
E.OLT
Stall prevention stop
V/F V/F V/F Magnetic flux Magnetic flux Magnetic flux
If the output frequency has fallen to 0.5 Hz by stall prevention operation and remains for 3 s, a
fault (E.OLT) appears and the inverter trips. OL appears while stall prevention is being activated.
Sensorless Vector Sensorless Sensorless Vector Vector PM PM PM
When speed control is performed, a fault (E.OLT) appears and the inverter trips if frequency
drops to the Pr. 865 "Low speed detection" (initial value is 1.5 Hz) setting by torque limit
operation and the output torque exceeds the Pr. 874 "OLT level setting" (initial value is 150%)
setting and remains 3 s.
Check the motor for the use under overload.
Check that the Pr. 865 and Pr. 874 values are correct.
(Check the Pr. 22 "Stall prevention operation level" setting under V/F control and Advanced
magnetic flux vector control.)
Check if a motor is connected under PM sensorless vector control.
Reduce the load.
Change the Pr. 22, Pr. 865, and Pr. 874 values. (Check the Pr. 22 setting under V/F control and
Advanced magnetic flux vector control.)
For a test run without connecting a motor, select the PM sensorless vector control test
operation. (Refer to page 5-60.)
Also check that the stall prevention (overcurrent) warning (OL) or the stall prevention
(overvoltage) warning (oL) countermeasure is taken.
E.SOT
PM PM PM
Loss of synchronism detection
The inverter trips when the motor operation is not synchronized. (This function is only available
under PM sensorless vector control.)
Check that the PM motor is not driven overloaded.
Check if a start command is given to the inverter while the PM motor is coasting.
Check if a motor is connected under PM sensorless vector control.
Check if a PM motor other than the MM-CF series is driven.
Set the acceleration time longer.
Reduce the load.
If the inverter restarts during coasting, set Pr. 57 "Restart coasting time" ≠ "9999", and select
the automatic restart after instantaneous power failure.
Check the connection of the IPM motor.
For a test run without connecting a motor, select the PM sensorless vector control test
operation. (Refer to page 5-60.)
Drive an IPM motor (MM-CF series)
When driving an IPM motor other than MM-CF series, offline auto tuning must be
performed. (Refer to page 5-454.)
Protective functions
FR-LU-08 Stall prevention STP
FR-LU-08 Motor step out