During a momentary power failure, the power of the external circuit (such as a relay circuit) controlling
the inverter also declines and the RUN command may also turn OFF. Therefore, when the operation
ready state is complete, the inverter waits for two seconds for the RUN command to be input. If the
input of the RUN command is confirmed within two seconds, the inverter starts restarting according to
Power Interruption Restart Mode Selection (F14). If the RUN command is not input, the restart mode
after momentary power failure is canceled, and startup is performed from the normal starting frequen-
cy.
Restart start
2s
Power failure time
Gate command ON
Inverter
status
RUN command
Gate OFF
Main Circuit
DC Voltage
Power failure Power restoration
Undervoltage level
Operation ready time
approx. 0.3 to 0.6 s
Operation ready completion
RUN command wait status
ON
ON
During power restoration, the inverter waits for two seconds for the RUN command to be input, but if
the time period set at Allowable Time for Power Interruption Restart (H16) elapses after power failure
is judged, the two-second long RUN command input waiting state is canceled, and normal startup is
performed.
If the free-run command “FRS” is input during a power failure, Free Run Stop Restart Operation Selec-
tion (H441) is set, and when the RUN command is input, startup is performed from the normal starting
frequency.
As a measure against dif
ficulty in bringing down the Main Circuit DC Voltage during momentary power
failure, if “22: IL (Interlock)” is allocated to Input Terminal [DI1] Function Selection to Input Terminal
[DI7] Function Selection (E01 to E05, E98, E99), the momentary power failure can be detected accu-
rately.
Input signal IL Meaning
OFF Momentary power failure not occurred
ON Momentary power failure occurred (Restart after momentary power failure enabled)
When the motor speed drops during momentary power failure and startup is performed from the fre-
quency prior to the momentary power failure after the power is restored, the current limitation function
is activated, and the output frequency of the inverter declines automatically. When the output frequen-
cy and the motor rotation speed are synchronous, acceleration is performed up to the original output
frequency.
However
, the momentary overcurrent limitation must be enabled (Instantaneous Overcurrent Limiting
Function Selection (H12) = 1) for the synchronous pull-in of the motor.
7 Other Functions
7-53
M1 Series Standard Type User's Manual (I669)
7-4 Restart Functions
7
7-4-2 Restart after Momentary Power Failure
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