7-2
Protective and Diagnostic Functions
This section describes the alarm functions of the Inverter. The alarm functions include fault detection, alarm
detection, operation error detection, and autotuning error detection.
îš‹ Fault Detection
When the Inverter detects a fault, the fault relay operates, and the Inverter output is switched OFF causing the
motor to coast to stop. (The stopping method can be selected for some faults.) A fault code is displayed on the
Digital Operator.
When a fault has occurred, refer to the following table to identify the fault and to correct the causes.
Use one of the following methods to reset the fault before restarting the Inverter:
• Set a multi-function digital input (H1-01 to H1-05) to 14 (Fault Reset) and switch the input ON.
• Press the Shift/RESET key on the Digital Operator.
• Turn the main circuit power supply OFF and then ON again.
• To reset a fault it is necessary to witch OFF the RUN command.
Table 7.1 Fault Detection
Display Meaning Probable Causes Corrective Actions
Overcurrent
The Inverter’s output current
exceeded the overcurrent detec-
tion level.
Shorted Inverter output phase-to-
phase, shorted motor, locked
rotor, load too heavy, accel/decel
time too short, contactor on the
Inverter output has opened or
closed, a special motor or a motor
with a rated current larger than
the Inverter’s output current is
used.
• Remove the motor and run
the Inverter without motor
• Check the motor for a phase
to phase short.
• Check the Inverter for a
phase to phase short at the
output.
• Verify the accel/decel time
settings
OC
Over Current
Ground Fault
The ground fault current at the
Inverter output exceeded approxi-
mately 50% of the Inverter rated
output current and L8-09=1
(Ground fault detection enabled)
One Inverter output was shorted
to ground and/or a DCCT is
defective.
• Remove the motor and run
the Inverter without motor.
• Check the motor for a phase
to ground short.
• Check the output current
with a clampmeter to verify
the DCCT reading.
GF
Ground Fault
DC Bus Fuse Blown
The fuse in the main circuit is
open.
Warning:
Never run the Inverter after
replacing the DC bus fuse with-
out checking for shorted compo-
nents
Shorted Inverter output and/or
damaged IGBTs
• Check the motor and motor
cables for short circuits or
insulation failures (phase to
phase
• Replace the Inverter after
correcting the cause.
PUF
DC Bus Fuse Open
DC Bus Overvoltage
The DC bus voltage has exceeded
the overvoltage detection level.
Refer to
page 6-100 for the OV
detection level.
• The deceleration time is too
short and the regenerative
energy from the motor is too
large.
• The power supply voltage is
too high.
• Increase the deceleration
time settings (C1-02/04/09)
or connect a braking option.
• Check the power supply
voltage and decrease the
voltage to meet the
Inverter’s specification.
OV
DC Bus Overvolt
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