8-8
Fault
display
Probable cause and remedyFault name and meaning
PF (See
note.)
Main circuit voltage fault
(PF)
The main circuit DC voltage
has oscillated erroneously
when regeneration was not
being performed.
This fault is detected when a
voltage fluctuation greater
than the input open-phase
detection level set in n166
persists for longer than the
input open-phase detection
time set in n167.
• Momentary power failure.
→ Either apply countermeasures against momentary power
failures or disable the input open-phase detection.
• Input power supply open phase.
→ Check for and correct any main circuit power supply
disconnections or faulty wiring.
• Excessive input power supply voltage fluctuation or bad line
voltage balance.
→ Check the power supply voltage. Apply measures to
stabilize the power supply, or disable the input
open-phase detection.
• Main circuit capacitor failure.
→ If this fault is occurring frequently and there is no error at
the power supply, replace the Inverter or disable the input
open-phase detection. (Also check the usage time with
the accumulated operating time function.)
LF (See
note.)
Output open-phase fault
(LF)
An open phase has occurred
at the Inverter’s output.
This fault is detected when a
current in any of the Inverter
output phases less than the
output open-phase detection
level set in n168 persists for
longer than the output
open-phase detection time set
in n169.
• Output cable is disconnected.
→ Check for and correct any output cable disconnections or
faulty wiring.
• Motor winding disconnected.
→ Check the motor’s line resistance. If winding is broken,
replace the motor.
• Output terminal screws are loose.
→ Check and tighten the output terminal screws.
• Inverter output transistor open breakdown.
→ Replace the Inverter.
GF (See
note.)
Ground fault (GF)
The ground current at the
Inverter has exceeded
approximately 50% of the
Inverter’s rated output current.
• Motor burnout or insulation damage.
→ Check the motor’s insulation resistance. If conducting,
replace the motor.
• Cable is damaged.
→ Check the resistance between the cable and FG. If
conducting, replace the cable.
• Cable and FG floating capacity
→ If the cable is longer than 100 m, lower the carrier
frequency.
→ Apply measures to reduce the floating capacity. Don’t use
metal ducts, use a separate cable for each phase,
include an AC reactor in the output side, etc.
SC (See
note.)
Load short circuit (SC)
The Inverter output or load is
short-circuited.
• Motor burnout or insulation damage.
→ Check the resistance between the motor phases. If
abnormal, replace the Inverter.
• Cable is damaged.
→ Check the resistance between the cables. If conducting,
replace the cable.
Maintenance Operations Chapter 8
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