Stall prevention stop
If the output frequency has fallen to 1 Hz by stall prevention operation and remains for 3 seconds, a fault (E.OLT)
appears and the inverter is shut off. OLC appears while stall prevention is being activated.
• Check if the motor is not used under overload.
• Reduce the load.
• Change the Pr.22 setting.
• Also check that the stall prevention (overcurrent) warning (OLC) or the stall prevention (overvoltage) warning
(OLV) countermeasure is taken.
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). Whether the protective function is used or not is set with Pr.249
Earth (ground) fault detection at start.
Check for a ground fault in the motor and connection cable.
• Remedy the earth (ground) fault portion.
• Check the Pr.249 setting.
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.
Whether the protective function is used or not is set with Pr.251 Output phase loss protection selection.
• Check the wiring. (Check that the motor is operating normally.)
• Check that the capacity of the motor used is not smaller than that of the inverter.
• Wire the cables properly.
• Check the Pr.251 setting.
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.182 (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.182 (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.
Parameter storage device fault
The inverter output is shut off if a fault occurs in the stored parameters. (EEPROM failure)
Check for too many number of parameter write times.
Contact your sales representative.
When performing parameter writing frequently for communication purposes, set "1" in Pr.342 Communication
EEPROM write selection to enable RAM write. Note that writing to RAM goes back to the initial status at power
Stall Prev STP
Output phase loss
Ext TH relay oper
PR storage alarm
6. PROTECTIVE FUNCTIONS
6.5 Causes and corrective actions