Protective And Diagnostic Functions; Fault Detection - Omron VARISPEED L7 Manual

Protective and Diagnostic Functions

This section describes the fault and alarm functions of the Inverter. These functions include fault detection,
alarm detection, programming error detection and auto-tuning error detection.

Fault Detection

When the Inverter detects a fault, the fault contact output is operated and the Inverter output is switched OFF
and the motor coasts to stop. (The stopping method can be selected for some faults.) A fault code is displayed
on the Digital Operator/LED Monitor.
The faults can be categorized in two groups:
Faults that can be reset without cycling the power using an input or the reset key at the Digital Operator
•
(resetable faults)
Faults that require to cycle the power (non-resetable faults)
•
When a fault has occurred refer to the following to identify the fault and to correct the causes.
To reset a fault it is necessary to remove the RUN signal and correct the fault reason. Otherwise a Reset is not
accepted or the Inverter trips with the same fault again.
The following tables shows a list of faults and corrective actions.
Display
GF
Ground Fault
7
OC
Over Current
PUF
DC Bus Fuse Open
2
7-
Table 7.1 Resetable Faults
Meaning
Ground Fault
The ground current at the Inverter out-
put exceeded 50% of the Inverter rated
output current and L8-09=1 (Enabled).
Overcurrent
The Inverter's output current exceeded
the overcurrent detection level.
DC Bus Fuse blown.
The fuse in the main circuit is open.
Warning:
Never run the Inverter after replacing
the DC bus fuse without checking for
shorted components.
Probable Causes
One Inverter output was shorted to
ground or a DCCT is defective.
The output contactor was opened when
the inverter output was still active.
Shorted Inverter output phase-to-phase,
shorted motor, locked rotor, too heavy
load, accel/decel time too short, contac-
tor 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.
Shorted output transistor(s) or
terminals.
Corrective Actions
Remove the motor and run the
Inverter without the motor.
Check the motor for a phase to
ground short.
Check the output current with a
clampmeter to verify the DCCT
reading.
Check the control sequence for
wrong motor contactor signals.
Remove the motor and run the
Inverter without the motor.
Check the motor for a phase-to-
phase short.
Verify the accel/decel times
(C1- ).
Check the Inverter for a phase-to-
phase short at the output.
Check the motor and the motor
cables for short circuits or insula-
tion failures (phase-to-phase).
Replace the inverter after correct-
ing the fault.