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12-4 Troubleshooting
OMNUC G5-series AC Servomotors and Servo Drives User’s Manual (with Built-in EtherCAT Communications)
  12
Troubleshooting and Maintenance
12-4 Troubleshooting
If an error occurs in the machine, determine the error conditions from the error displays and
operation state, identify the cause of the error, and take appropriate measures.
Troubleshooting with Error Displays
Error List
Error No. (hex)
Name Cause Measures
Main Sub
11 0
Control 
Power Supply 
Undervoltage
The voltage between the positive and 
negative terminals in the control power 
supply converter dropped below the 
specified value.
• The power supply voltage is low. A 
momentary power interruption occurred.
• Insufficient power supply capacity: the 
power supply voltage dropped because 
there was inrush current when the main 
power supply was turned ON.
• The Servo Drive is faulty (circuit fault).
Measure the voltage between the L1C 
and L2C lines on the connectors and the 
terminal block.
• Increase the power supply voltage. 
Change the power supply.
• Increase the power supply capacity.
• Replace the Servo Drive.
12 0
Overvoltage The power supply voltage exceeded the 
allowable input voltage range, causing the 
voltage between the positive and negative 
terminals in the converter to exceed the 
specified value. The power supply voltage 
is high. The voltage was suddenly 
increased by the phase advance capacitor 
or the uninterruptible power supply (UPS).
• The Regeneration Resistor wiring is 
broken.
• The External Regeneration Resistor is 
inappropriate and cannot absorb all of 
the regenerative energy. The load 
inertia is too large, gravitational torque 
on the vertical axis is too large, or there 
is some other problem to absorb the 
regenerative energy. 
• The Servo Drive is faulty (circuit fault).
Measure the voltage between the 
connector (L1, L2, and L3) lines. Input the 
correct voltage. Remove the phase 
advance capacitor.
• Use a tester to measure the resistance 
of the external resistor between the B1 
and B2 terminals on the Servo Drive. If 
the resistance is infinite, the wiring is 
broken. Replace the external resistor.
• Change the regeneration resistance and 
wattage to the specified values. 
(Calculate the regenerative energy and 
connect an External Regeneration 
Resistor with the required regeneration 
absorption capacity. Reduce the 
descent speed.)
• Replace the Servo Drive.