8-3
Fault
display
Probable cause and remedyFault name and meaning
%U
Overvoltage (OV)
The main circuit DC voltage
has reached the overvoltage
detection level (410 V DC for
200-V Inverters,
820 V DC for 400-V Inverters)
• There is excessive regenerative energy with no braking
resistor or Braking Resistor Unit connected.
→ Connect the Braking Resistor Unit or a braking resistor.
→ Increase the deceleration time.
• The regenerative energy has not been processed though a
braking resistor or Braking Resistor Unit.
→ Set n092 for stall prevention during deceleration to 1
(disable)
• The braking resistor or Braking Resistor Unit is not wired prop-
erly.
→ Check and correct the wiring.
• The power supply voltage is too high.
→ Decrease the voltage so it will be within specifications.
• There is excessive regenerative energy due to overshooting
at the time of acceleration.
→ Suppress the overshooting as much as possible.
• The braking transistor is damaged.
→ Change the Inverter.
uU1
Main circuit undervoltage
(UV1)
The main circuit DC voltage
has reached the undervoltage
detection level (200 V DC for
the 3G3MV-A2j, 160 V DC
for the 3G3MV-ABj, and 400
V DC for the 3G3MV-A4j).
• Power supply to the Inverter has phase loss, power input
terminal screws are loose, or the power cable is discon-
nected.
→ Check the above and take necessary countermeasures.
• Incorrect power supply voltage
→ Make sure that the power supply voltage is within
specifications.
• Momentary power interruption has occurred.
→ Use the momentary power interruption compensation
(Set n081 so that the Inverter restarts after power is
restored)
→ Improve the power supply.
• The internal circuitry of the Inverter is damaged.
→ Change the Inverter.
uU2
Control power supply
undervoltage (UV2)
The control power supply
voltage has reached the
undervoltage detection level.
• Internal circuit fault.
→ Turn the Inverter OFF and ON.
→ Change the Inverter if the same fault occurs again.
Maintenance Operations Chapter 8
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