Chapter 5 Maintenance
5 – 2
5.2 Product Life
The lifetime of electrolytic capacitors used in the power module is limited. Electrolytic capacitors are used in some of
I/O modules to improve noise resistance. If the lifetime is exceeded, performance of product is not guaranteed. Be sure
to conduct inspection and maintenance as follows.
(1) Power module
Many electrolytic capacitors are used in the power module. It is said that lifetime of electrolytic capacitor
would be half when ambient temperature increases 10 °C.
If lifetime of electrolytic capacitor is exceeded, output power becomes unstable especially when output current
is high due to many point of outputs are activated for example.
Prepare spare units with considering 5 years lifetime in case ambient temperature is 30°C. For longer lifetime,
take account of installation location in terms of temperature and air circulation around power unit and.
(2) CPU module
Some electrolytic capacitors are used in CPU module also. I If lifetime of electrolytic capacitor is exceeded,
more errors could happen since noise resistance is not enough. Be sure to overhaul CPU module periodically.
CPU module has a battery to maintain realtime clock data and retain memory. Be noted following points about
lifetime of battery.
- The battery life as shown below is total power failure time of PLC.
- When ERR LED blinks and error code 71 is displayed, replace a battery to new one.
As a guideline, replace a battery every two years even when the total power failure time is less than the
guaranteed value shown in the table.
Battery life (Total power failure time)[Hr]
Guaranteed value (MIN) @55°C
Actual value (MAX) @25°C
2,000 17,700
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