Chapter 9 PLC Operation

9.3 Instantaneous Power Failure

The following shows operation when the power supply to the MICRO-EH shuts off.

AC power supply

Internal 5 V DC

Internal reset

24 V DC

RUN

ON

OFF

MICRO-EH operation

 

 

 

 

 

 

Instantaneous power failure

 

 

 

 

 

 

 

 

 

 

 

RUN status

 

 

 

STOP status

(Starts operation)

 

Reset processing

 

When power supply of 100 V AC is used:

Power on

 

1.0 s

 

 

operation continues for 10 ms or less

 

 

When power supply of 200 V AC is used:

2 s

 

 

 

 

 

 

 

 

1.2 s

 

operation continues for 20 ms or less

 

 

 

(1)Powering on

The MICRO-EH starts operations after a maximum of 3.5 seconds have elapsed after power-up. If the power for input module is not completely started when the operation is commenced, the input that is supposed to be on will be received as Off and operation proceeds, so make sure that the power for I/O module is completely turned on before operation is commenced.

Note: When extending with a CPU larger than 14-point type, turn on the power supply for both base and extension sides at the same time.

(2)Instantaneous power failure actions

(a)When 100 VAC is supplied

Operation is continued during instantaneous power failures that last less than 10 ms.

(b)When 200 VAC is supplied

Operation is continued during instantaneous power failure that last less than 20 ms.

Note: Make arrangement so that the power for input module is supplied while the CPU continues its operation. If the power is not supplied, the CPU will perform operation assuming the input data as Off. Exercise caution especially when performing operation that changes the contents of the power failure memory using input signals, since the contents of the power failure memory may have been altered unintentionally due to an instantaneous power failure.

9-10

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Hitachi NJI-350B manual Instantaneous Power Failure, Powering on, Instantaneous power failure actions, Run Off