Product Life Of Relay Contacts - Mitsubishi FX3U SERIES User Manual

FX Series Programmable Controllers
3U
User's Manual - Hardware Edition
4.4.2

Product life of relay contacts

The product life of relay contacts varies considerably depending on the load type used. Take care that loads
generating reverse electromotive force or rush current may cause poor contact or deposition of contacts
which may lead to considerable reduction of the contact product life.
1. Inductive load
Inductive loads generate large reverse electromotive force between contacts at shutdown, which may cause
arcing. At a fixed current consumption, as the power factor (phase between current and voltage) gets smaller,
the arc energy gets larger.
The standard life of contacts used for Inductive loads, such as contactors and solenoid valves, is 500,000
operations at 20VA.
The following table shows the approximate life of a relay based on the results of an operation life test.
Test condition: 1 sec. ON / 1 sec.OFF
Load capacity
0.2 A / 100V AC
20 VA
0.1 A / 200V AC
0.35 A / 100V AC
35 VA
0.17 A / 200V AC
0.8 A / 100V AC
80 VA
0.4 A / 200V AC
The product life of relay contacts becomes considerably shorter than the above conditions when the rush
overcurrent is shut down.
Some types of inductive loads generate rush current 5 to 15 times the stationary current at activation. Make
sure that the rush current does not exceed the current corresponding to the maximum specified resistance
load.
2. Lamp load
Lamp loads generally generate rush current 10 to 15 times the stationary current. Make sure that the rush
current does not exceed the current corresponding to the maximum specified resistance load.
3. Capacitive load
Capacitive loads can generate rush current 20 to 40 times the stationary current. Make sure that the rush
current does not exceed the current corresponding to the maximum specified resistance load. Capacitive
loads such as capacitors may be present in electronic circuit loads including inverters.
54
4 Specifications, External Dimensions and Terminal Layout (Main Units)
Contact life
3,000,000 times
1,000,000 times
200,000 times
→ For precautions on using inductive loads, refer to Subsection 12.2.4 2.
→ For the maximum specified resistance load, refer to Subsection 4.4.1.
4.4 Output Specifications