Appendices
A-52
NJ-series CPU Unit Hardware User’s Manual (W500)
The service life expectancy of the relays (NY-24W-K-IE) in the CJ1W-OC201/211 Contact Output
Units depends on the type of load, the contact current, and the ambient temperature. Use the follow-
ing diagrams to calculate the relay service life based on the operating conditions, and replace the
relay before the end of its service life.
Precautions for Correct UsePrecautions for Correct Use
The above charts show the life characteristics for the individual relays. Do not exceed the speci-
fications of the Relay Output Units. If a switching capacity exceeding the specifications is used,
the reliability and life expectancy of other parts will be reduced and the Unit may malfunction.
The life of the Relay varies with the load inductance. If any inductive load is connected to the Con-
tact Output Unit, use an arc killer with the Contact Output Unit. (See next page.)
Be sure to connect a diode in parallel with every DC inductive load that is connected to the Contact
Output Unit. The usage of an arc killer has a significant effect on the service life of the contacts.
Arc killers are used with the Contact Output Unit in order to prolong the life of each Relay mounted
to the Contact Output Unit, prevent noise, and reduce the generation of carbide and nitrate deposits.
However, if arc killers are used incorrectly, they can reduce relay life. Using an arc killer can also
cause a delay in the resetting time (shut-off time). Arc killer circuit examples are listed in the follow-
ing table.
A-2-3 Precautions on Contact Output Units
Service Life Expectancy
Contact Current vs. Service Life Characteristic
Inductive Load
Contact Protection Circuit
0.1 0.2 0.3 0.5 1 2 3 50.7
2
3
5
10
20
30
50
100
200
300
0.1 0.2 0.3 0.5 1 2 3 5 0.7
2
3
5
10
20
30
50
100
200
300
0.05
Service Life with AC Load
Service Life with DC Load
120 VAC, resistive load
240 VAC, resistive load
120 VAC cos f = 0.4
240 VAC cos
φ
= 0.4
Service life (
×
10
4
)
Service life (
×
10
4
)
Contact current (A)
Contact current (A)
24 VDC, resistive load
24 VDC
τ
= 7 ms
Switching frequency: 1,800 operations/hour max.
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