5.1 Errors (Alarms)
5 PROTECTIVE FUNCTIONS
5.1 Errors (alarms)
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
Instantaneous power failure
Brake transistor alarm
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When the inverter output current reaches or exceeds approximately
200% of the rated current, the protective circuit is activated to stop the
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 more 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 seconds)
If a power failure has occurred in excess of 15ms (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-C)
(Note 1). If a power failure persists for more than 100ms, the alarm
output is not provided, if the start signal is on at the time of power
restoration, the inverter will restart. (If a power failure is instantaneous
within 15ms, the control circuit operates properly.)
•If the inverter power supply voltage reduces, the control circuit will not
operate properly, resulting in decreased motor torque or increased
heat generation. To prevent this, if the power supply voltage reduces
below 150V (about 300V for the 400V class), this function stops the
•When a jumper is not connected across P-P1 〈+ -P1〉, the undervoltage
protective function is activated.
If the cooling fin overheats, the temperature sensor is activated to stop
the inverter output.
For the inverter which contains a cooling fan, FN is displayed on the
operation panel and the fan fault signal (FAN) and light fault signal (LF)
are output when the cooling fan stops due to a fault or operates
differently from the setting of Pr. 244 "cooling fan operation selection".
If the brake circuit fault has occurred due to damaged brake transistors,
etc., this function stops the inverter output.
In this case, the inverter power must be switched off immediately.