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7-2
(4) Overvoltage
Overvoltage
during acceleration
OU1
Overvoltage
running at constant speed
OU3
Overvoltage
during deceleration
OU2
Reduce the supply voltage
to less than the specified
upper limit.
NO
Is the power supply voltage within the specified value?
Is start mode(H09) activated and its start-mode?
YES YES YES
NONONO
NONONO
YES
NO
NO
NO
NO
YES
Can the deceleration time be prolonged?
Reduce.
NO
Does OU alarm activate
when acceleration
is completed?
NO
YES
YES
Prolong.
NO
Can the acceleration
time be prolonged?
NO
Faulty inverter
or error due to noise.
Contact Fuji Electric.
NO
Does the main circuit DC link circuit
voltage exceed the protection level?
Can the moment of load inertia be reduced?
NO
NO
YES
Is the braking device or DC brake function in use?
Inspect the braking method. Contact Fuji Electric.
YES
YES
YES YES YES
NO
Is restart mode after momentary power failure or
operation switching between line and inverter?
Does OU activated when the load is suddenly removed?
YES
Consider using
a braking system
or DC brake function.
YES
Restart time(H13) is
set longer.
YES
Check the motor and /or
the terminal(U, V, W)
is shorted or ground fault.
(5) Low voltage
NO
NO
YES
YES
Low voltage
LU
Reset and restart
operation.
Replace the faulty part
and repair the connection.
Modify power distribution system
to satisfy the specified value.
Is power transformer
capacity adequate?
The inverter may be faulty.
Contact Fuji Electric.
Has a (momentary) power
failure occurred?
Faulty parts or loose
connection in the
power circuit?
NO
Is the power supply
voltage within the
specified value?
YES
Does LU activate when
the circuit breaker or
magnetic contactor is
switched on?
Faulty of inverter control
circuit or error due
to noise, etc.
Contact Fuji Electric.
Is there a load requiring
a large starting current
within the same power
distribution group?
YES
NO
YES
Is the main circuit DC voltage
(between P-N) higher than
the detection level specified
in Section 6.1.1?
NONOYES
YES