11-12
11-4 Troubleshooting
OMNUC G5-SERIES AC SERVOMOTOR AND SERVO DRIVE USER'S MANUAL
  11
Troubleshooting and Maintenance
13
0
Main power supply 
undervoltage 
(insufficient voltage 
between P and N)
If the Undervoltage Error Selection 
(Pn508) is set to 1, a momentary 
power interruption occurred between 
L1 and L3 for longer than the value 
specified for the Momentary Hold 
Time (Pn509). Or, the voltage 
between the positive and negative 
terminals in the control power supply 
converter dropped below the 
specified value while the Servo was 
ON.
100-V models: Approx. 80 VDC 
(approx. 55 VAC)
200-V models: Approx. 110 VDC 
(approx. 75 VAC)
400-V models: Approx. 180 VDC 
(approx. 125 VAC)
· 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.
· Phase loss: A Servo Drive with 3-
phase input specification was 
operated with a single-phase 
power supply.
· The Servo Drive has failed (circuit 
failure).
Measure the voltage between the L1, 
L2, and L3 lines on the connector and 
the terminal block.
· Increase the power supply voltage 
capacity. Change the power 
supply.
· Eliminate the cause of the failure 
of the electromagnetic contactor 
on the main circuit power supply, 
and then turn ON the power again.
· Check the setting of the 
Momentary Hold Time (Pn509). 
Correctly set the phases of the 
power supply.
· Increase the power supply 
capacity. Refer to Servo Drive and 
Servomotor Combination Tables 
on page 2-11  for information on 
the power supply capacity.
· Connect the phases (L1, L2, L3) of 
the power supply correctly. Use L1 
and L3 for single-phase 100 V and 
single-phase 200 V.
· Replace the Servo Drive.
1
Main power supply 
undervoltage (AC cut-
off detection)
Alarm 
number
Name Cause Measures
Main Sub