*3. Resetting the inverter initializes the internal heat integrating data of the electronic thermal relay function.
4: When an instantaneous power failure occurs, the alarm display and alarm output are not provided, but the
inverter performs protective operation to prevent a fault from occurring in itself. In some operating status (load
magnitude, acceleration/deceleration time setting, etc.), overcurrent or other protection may be activated upon
Inverter overload shut-off (electronic thermal relay function) (*3)
If a current not less than 150% of the rated output current flows and overcurrent shut-off does not
occur (200% or less), inverse-time characteristics cause the electronic thermal relay function to be
activated to stop the inverter output in order to protect the output transistors.
Protection of output transistors against overheat.
Check the motor for use under overload.
Reduce the load weight.
Instantaneous power failure protection (*4)
If a power failure occurs for longer than 15ms (this also applies to inverter input shut-off), the
instantaneous power failure protective function is activated to stop the inverter output in order to
prevent the control circuit from malfunctioning. At this time, the alarm warning output contacts open
(across terminals B-C) and close (across terminals A-C). If a power failure persists for longer than
100ms, the alarm warning output is not provided, and the inverter restarts if the start signal is on
upon power restoration. (The inverter continues operating if an instantaneous power failure is
Find the cause of instantaneous power failure occurrence.
• Remedy the instantaneous power failure.
• Prepare a backup power supply for instantaneous power failure.
• Set the function of automatic restart after instantaneous power failure (Pr. 57).
(Refer to page 114.)
If the power supply voltage of the inverter reduces, the control circuit will not perform normal
functions. In addition, the motor torque will be insufficient and/or heat generation will increase. To
prevent this, if the power supply voltage reduces below about 618VDC, this function stops the
When a jumper is not connected across P-P1, the undervoltage protective function is activated.
• Check for start of large-capacity motor.
• Check that a jumper or DC reactor is connected across terminals P-P1.
• Check the power supply system equipment such as power supply.
• Connect a jumper or DC reactor across terminals P-P1.
If the heatsink overheats, the temperature sensor is actuated to stop the inverter output.
• Check for too high ambient temperature.
• Check for heatsink clogging.
• Check that the cooling fan is stopped.
• Set the ambient temperature to within the specifications.
• Replace the cooling fan.
Brake transistor alarm detection
This function stops the inverter output if an alarm occurs in the brake circuit, e.g. damaged brake
In this case, the inverter must be powered off immediately.
• Reduce the load inertia.
• Check that the frequency of using the brake is proper.
• Check that the brake resistor selected is correct.
Replace the inverter.
Inst. Pwr. Loss
Br. Cct. Fault