YASKAWA P7, User Manual, Page: 151 / 256

Diagnostic & Troubleshooting 6 - 7
UV1
DC Bus Undervolt
DC Bus Undervoltage
The DC bus voltage is
≤
L2-05
208-240Vac: Trip point is
≤
190Vdc
480Vac: Trip point is
≤
380Vdc
Low input voltage at R/L1,
S/L2 and T/L3
Check the input circuit and
increase the input power to within
specifications
The acceleration time is set too
short
Extend the time in C1-01
Voltage fluctuation of the input
power is too large
Check the input voltage
UV2
CTL PS Undervolt
Control Power Supply Undervoltage
Undervoltage of the control circuit when
running
External load connected
pulling down the Drive power
supplies
Cycle power off and on to the
Drive
Repair or replace the Power PCB/
Gate Drive PCB
Remove all control wiring and
test Drive
UV3
MC Answerback
Soft Charge Circuit Fault
The pre-charge contactor opened while the
Drive was running
Contacts on the soft charge
contactor are dirty and the soft
charge contactor does not
function mechanically
Cycle power off and on to the
Drive
Check the condition of the soft
charge contactor
Repair or replace the Power PCB/
Gate Drive PCB
WARNING
Some features within the PI function group, cause the Drive to shut down momentarily (e.g. Sleep Function,
Snooze Function, Feedback Loss feature etc.) Upon recovery from the conditions that activate these features,
the Drive may start unexpectedly. Therefore, when enabling these features take appropriate measures to
notify personnel working with this equipment that unexpected starting may occur.
Table 6.1 Fault Displays and Processing
Digital
Operator Display
Description Cause Corrective Action