5.1 Errors (Alarms)
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If any fault has occurred in the inverter, the corresponding protective function is activated and the error (alarm)
indication appears automatically on the PU display. When the protective function is activated, refer to "5.2
Troubleshooting" and clear up the cause by taking proper action. If an alarm stop has occurred, the inverter must
be reset to restart it.
5.1.1 Error (alarm) definitions
Acc
acceleration
OC
speed
Dec
deceleration
During stop
When the inverter output current reaches or exceeds approx. 200% of
the rated current, the protective circuit is activated to stop the inverter
Acc
acceleration
OV
speed
Dec
deceleration
During stop
If regenerative energy from the running motor causes the inverter's
internal main circuit DC voltage to reach or exceed the specified value,
the protective circuit is activated to stop the inverter output.
This may also be activated by a surge voltage generated in the power
The electronic overcurrent protection in the inverter detects motor
overheat due to overload or cooling capability reduced during constant-
speed operation. When 85% of the preset value is reached, pre-alarm
(TH indication) occurs. When the specified value is reached, the
protective circuit is activated to stop the inverter output. When a special
motor such as a multi-pole motor or more than one motor is run, the
motor cannot be protected by the electronic overcurrent protection.
Provide a thermal relay in the inverter output circuit.
If a current not less than 150% of the rated output current flows and
overcurrent shut-off (OC) does not occur (200% or less), inverse-time
characteristics cause the electronic overcurrent protection to be
activated to stop the inverter output. (Overload immunity: 150%, 60 sec)
At low-speed regions, the operation time may be short.
Instantaneous power failure
If a power failure has occurred in excess of 15msec (this applies also
to inverter input shut-off), this function is activated to stop the inverter
output to prevent the control circuit from misoperation. At this time, the
alarm output contacts are opened (across B-C) and closed (across A-
(Note 1) If a power failure persists for more than 100ms, the alarm
output is not provided, and if the start signal is on at the time of power
restoration, the inverter will restart. (If a power failure is instantaneous
within 15msec, the control circuit operates properly.)
If the inverter power supply voltage drops, the control circuit will not
operate properly. Furthermore, the motor torque could drop and the heat
generated may increase. The inverter output will be stopped if the
power supply voltage drops to 150V (approx. 300V for 400V class) or
The undervoltage protection function will activate if the DC reactor
If the cooling fin overheats, the temperature sensor is activated to stop
