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If you enable the "Restart mode after momentary power failure" (Function code F14 = 3, 4, or 5), the inverter
automatically restarts the motor running when the power is recovered. Design the machinery or equipment so
that personnel safety is ensured after restarting.
Otherwise an accident could occur.
Restart mode after momentary power failure (Basic operation with auto search disabled)
The inverter recognizes a momentary power failure upon detecting the condition that DC link bus voltage goes
below the undervoltage detection level, while the inverter is running. If the load of the motor is light and the
duration of the momentary power failure is extremely short, the voltage drop may not be great enough for a
momentary power failure to be recognized, and the motor may continue to run uninterrupted.
Upon recognizing a momentary power failure, the inverter enters the restart mode (after a recovery from
momentary power failure) and prepares for restart. When power is restored, the inverter goes through an initial
charging stage and enters the ready-to-run state. When a momentary power failure occurs, the power supply
voltage for external circuits such as relay sequence circuits may also drop so as to disable the run command. If
this occurs, the inverter waits 2 seconds for a run command input after the inverter enters a ready-to-run state.
When received; the inverter begins the restart processing in accordance with the F14 data (Mode selection). If no
run command has been received within 2-seconds, the inverter cancels the restart mode (after a recovery from
momentary power failure) and needs to be started again at starting frequency. Therefore, ensure that a run
command is entered within 2 seconds after a recovery of power, or install a mechanical latch relay.
When starting and stopping via the keypad (F02=0), the above operation will also apply regardless of the whether
FWD, REV, or F02 = 2 or 3 sets rotational direction.
• When the power is restored, the inverter will wait up to 2 seconds for a run command. However, the
setting of H16 (allowable momentary power failure supply) overrides the 2 second limit if set below 2
seconds.
• If the "Coast to a stop" terminal command
BX
is entered during the power failure, the inverter exits the
restart mode and enters the normal running mode. If a run command is entered with power applied, the
inverter will start from the normal starting frequency.
• The inverter recognizes a momentary power failure by detecting an undervoltage condition whereby the
voltage of the DC link bus goes below the lower limit. In a configuration where a magnetic contactor is
installed on the output side of the inverter, the inverter may fail to recognize a momentary power failure
because it also may shut down the operating power of the magnetic contactor, causing the contactor
circuit to open. If this occurs, the inverter is cut off from the motor and load, and the voltage drop in the
DC link bus is not great enough to be recognized as a power failure. In such an event, restart after a
recovery from momentary power failure does not work properly as designed. To remedy this, connect
the interlock command
IL
line to the auxiliary contact of the magnetic contactor, so that a momentary
power failure can sure be detected. For details, refer to the descriptions of E01 through E07.
Function code E01 to E07, data = 22
IL
Description
OFF
No momentary power failure has occurred.
ON
A momentary power failure has occurred. (Restart after a momentary power failure enabled)