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Chapter 10 PLC Installation, Mounting, Wiring
10-7
(a) Wiring to the relay output terminals
1] Life of relay contacts
Life curve of relay contacts
500
100
10
1
01 45
50
20
63
2
1000
AC 125 V cos φ =1
AC 125 V cos φ =0.7
AC 125 V cos φ =0.4
Switching life (10,000 times)
Contact switchin
g
current
(
A
)
Figure 1 Life characteristics (125 V AC)
Life of the contact is almost in squared
reverse proportion to the current, so be aware
that interrupting rush current or directly
driving the condenser load will drastically
reduce the life of the relay.
When switching is made with high
frequency, use a transistor output module.
500
100
10
1
01 45
50
20
63
2
1000
AC 250 V cos φ =1
AC 250 V cos φ =0.7
AC 250 V cos φ =0.4
Contact switchin
g
current
(
A
)
Figure 2 Life characteristics (250 V AC)
Switching life (10,000 times)
500
100
10
1
01 45
50
20
63
2
1000
DC 30 V L/R=1 ms
DV 30 V L/R=7 ms
DC 30 V L/R=15 ms
Figure 3 Life characteristics
Switching life (10,000 times)
Contact switchin
g
current
(
A
)
2] Surge killer
For inductive load, connect a surge killer (condenser 0.1 µF, + resistance of approx. 100 Ω) in parallel to
the load. Also, for DC load, connect a flywheel diode.
3] Fuse
A built-in fuse is not used in this module. Install a 6 A fuse in the common to prevent the external wiring
from burning out.
For the independent contact output section, install a 2A fuse per circuit.
(b) Wiring to the transistor output terminals
4] Flywheel diode
For inductive load, connect a flywheel diode in parallel.
5] V and C terminals
Always connect a V terminal and C (common) terminal. If the module is used without connecting these
terminals, the internal flywheel diode may not function and the module may malfunction or break down.
6] Fuse
There is no built-in fuse to prevent external wiring burning. Therefore, it is recommended that a fuse be
installed externally to prevent the external wiring from burning out. (This does not protect the internal
transistor elements.) If the external load is short-circuited, please contact us for repair.