Safety Measures; Momentary Power Failures - Panasonic FP E Series User Manual

5.6 Safety Measures

5.6.1 Safety Measures
Precautions regarding system design
In certain applications, malfunction may occur for the following reasons:
• Power on timing differences between the PLC system and input/output or mechanical power apparatus.
• Response time lag when a momentary power drop occurs.
• Abnormality in the PLC unit, external power supply, or other devices.
In order to prevent a malfunction resulting in system shutdown choose the adequate safety measures
listed in the following:
Interlock circuit
When a motor clockwise/counter-clockwise operation is controlled, provide an interlock circuit externally.
Emergency stop circuit
Provide an emergency stop circuit to the PLC externally to turn off the power supply of the output device.
Start up sequence
The PLC should be operated after all of the outside devices are energized. To keep this sequence, the
following measures are recommended:
• Turn on the PLC with the mode selector set to the PROG. mode, and then switch to the RUN mode.
• Program the PLC so as to disregard the inputs and outputs until the outside devices are energized.
Note) In case of stopping the operation of the PLC also, have the input/output devices turned off after
the PLC has stopped operating.
Grounding
When installing the PLC next to devices that generate high voltages from switching, such as inverters,
do not ground them together. Use an exclusive ground for each device.

5.6.2 Momentary Power Failures

Operation of momentary power failures
If the duration of the power failure is less than 3 ms, the FPΣ continues to operate. If the power is off for
3 ms or longer, operation changes depending on the combination of units, the power supply voltage, and
other factors. (In some cases, operation may be the same as that for a power supply reset.)
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