Causes and corrective actions
6 - 22
Undervoltage (Standard 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 V AC (300 V AC for the 400 V
class) or below, this function shuts off the inverter output.
When a jumper is not connected across P/+ and P1, the undervoltage protective function is
When undervoltage protection is activated, the IPF signal is output.
(Refer to page 5-415, page 5-423.)
Check if a high-capacity motor is driven.
Check if the jumper is connected across terminals P/+ and P1.
Check the power supply system equipment such as the power supply.
Do not remove the jumper across terminals P/+ and P1 except when connecting a DC
If the problem still persists after taking the above measure, contact your sales
Input phase loss (Standard models only)
When Pr. 872 "Input phase loss protection selection" is enabled ("1") and one of the three-phase
power input is lost, the inverter output is shut off. This protective function is not available when
Pr. 872 is set to the initial value (Pr. 872 = "0"). (Refer to page 5-163)
Check for a break in the cable for the three-phase power supply input.
Wire the cables properly.
Repair a break portion in the cable.
Stall prevention stop
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.
During speed control, a fault (E.OLT) appears and the inverter trips if the frequency value
converted from the motor rotation speed drops to 1.5 Hz or lower by stall prevention operation
and the output torque exceeds the Pr. 874 "OLT level setting" (refer to page 5-180) and remains
there for 3 s.
Check the motor for the use under overload.
Check that the 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 motor control.
Reduce the load.
Change the Pr. 22, 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 motor control test operation. (Refer
to page 5-42.)
Also check that the stall prevention (overcurrent) warning (OL) or the stall prevention
(overvoltage) warning (oL) countermeasure is taken.
Input phase loss
Stall prevention STP