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  • No : 22587
  • Release Date : 2018/09/03 17:29
  • Update : 2018/09/20 17:41
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Behavior of sequence program in event of momentary power failure in QCPU

Which status do sequence programs become in case of momentary power failure?
Category : 

Answer

(1) When a momentary power failure occurs for a period not longer than the allowable momentary power failure time
     When the momentary power failure occurs, the module records an error log and suspends the operation processing.
     However, measurement in the timer device is continued. Also, the output status is held.
     - When resume start is specified for the SFC program, data in the system is saved.
     - When the power is recovered from the momentary power failure, the module resumes the operation processing.
     - Even if operation processing is suspended due to a momentary power failure, the measurement of the watchdog timer
       (WDT) is continued.

(2) When a momentary power failure occurs for a period longer than the allowable momentary power failure time.
     The CPU module performs an initial start.The operation processing is the same as the following.
     - Power-on of the programmable controller
     - Reset operation
     - Remote reset operation by programming tool

In a redundant power supply module, if a momentary power failure occurs in either of the power supply modules,
operations are not suspended.
However, if a momentary power failure occurs under the condition where the power is supplied to only one of the
power supply modules, operations are suspended.
Product Name
MELSEC-Q Series
Series
CPU
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