10-12
10.4 If an Alarm Code Appears on the LED Monitor
[ 1 ]
Instantaneous overcurrent
Problem The inverter momentary output current exceeded the overcurrent level.
Overcurrent occurred during acceleration.
Overcurrent occurred during deceleration.
Overcurrent occurred during running at a constant speed.
Possible Causes
What to Check and Suggested Measures
(1) The inverter output lines were
short-circuited.
Disconnect the wiring from the inverter output terminals ([U], [V] and [W]) and
measure the interphase resistance of the motor wiring. Check if the resistance
is too low.
Remove the short-circuited part (including replacement of the wires, relay
terminals and motor).
(2) Ground faults have occurred at
the inverter output lines.
Disconnect the wiring from the output terminals ([U], [V] and [W]) and perform
a Megger test.
Remove the grounded parts (including replacement of the wires, relay
terminals and motor).
(3) Overload.
Measure the motor current with a measuring device to trace the current trend.
Then, use this data to judge if the trend is over the calculated load value for
your system design.
If the load is too heavy, reduce it or increase the inverter capacity.
Trace the current trend and check if there are any sudden changes in the
current.
If there are any sudden changes, make the load fluctuation smaller or
increase the inverter capacity.
Enable instantaneous overcurrent limiting (H12 = 1).
(4) Excessive torque boost
specified.
(when F37* = 0, 1, 3, or 4)
Check whether decreasing the torque boost (F09*) decreases the output
current but does not stall the motor.
If no stall occurs, decrease the torque boost (F09*).
(5) The acceleration/ deceleration
time was too short.
Check that the motor generates enough torque required during
acceleration/deceleration. That torque is calculated from the moment of
inertia for the load and the acceleration/deceleration time.
Increase the acceleration/deceleration time (F07, F08, E10 through E15,
and H56).
Enable the current limiter (F43) and torque limiter (F40, F41, E16, and
E17).
Increase the inverter capacity.
(6) Malfunction caused by noise.
Check if noise control measures are appropriate (e.g., correct grounding and
routing of control and main circuit wires).
Implement noise control measures. For details, refer to the EQ7 User's
Manual, "Appendix A."
Enable the Auto-reset (H04).
Connect a surge absorber to magnetic contactor's coils or other solenoids
(if any) causing noise.
[ 2 ]
Ground fault
Problem A ground fault path exists from the output terminal of the inverter.
Possible Causes
What to Check and Suggested Measures
(1) Inverter output terminal(s)
grounded (ground fault).
Disconnect the wiring from the output terminals ([U], [V], and [W]) and perform a
Megger test.
Remove the grounded parts (including replacement of the wires, relay
terminals and motor).
