9. Fault Diagnosis
215
Protective
Operation
Output is
turned OFF
and motor
coasts to a
stop.
PF (Main circuit voltage
fault)
The main circuit’s DC
voltage oscillated in an ir-
regular way when not in
regenerative operation.
• Open phase of input
supply
• Momentary
power
loss
• Excessive
fluctua-
tion in input supply
voltage
• Unbalanced
line
voltage
⇓
Check the following:
• Main circuit power
supply connections
• Power
supply
volt-
age
• Terminal
screws:
Loose?
LF (Output open phase)
An open phase occurred
in Inverter output.
• Disconnection
in
output cable
• Disconnection
in
motor windings
• Loose output termi-
nal screws
⇓
Check the following:
• Disconnection
in
output wirings
• Motor
impedance
• Terminal
screws:
Loose?
UL3 (Undertorque detec-
tion)
When V/f mode is select-
ed: The Inverter’s output
current was less than the
Undertorque Detection
Level (n118).
When vector mode is se-
lected:
The output current or out-
put torque was less than
the detection level (n097
to n118).
Operation when
undertorque is detected
will be determined by the
setting in n117.
• Check the setting in
n118.
• Check
the
operating
conditions, and
remove the cause.
Fault Display
Inverter
Status
Description
Causes and Correc-
tive Actions
Digital
Operator
RUN (Green)
ALARM (Red)
