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Section 4 Installation and Wiring
4-1-3 Control panel mounting (protection against noise)
The SPF series products are especially immure to noise pickup. However, it is always recommended to take the following
measures to further enhance system reliability.
N
. o
C
a
u
s
e
f o
n
o
s i
e
1
Noise via power-supply terminals
• Lightning surge
• Internal surge (switching surge)
2
H
g i
h
f -
e r
q
u
e
n
y c
n
o
3
N
o
s i
e
n i
p
t u
v
a i
c
o
m
Other device
Common ground must not be used.
4
Noise via ground of the secondary coils of a transformer
s i
e
m
o
n
g
o r
u
n
d
n i l
e
Other device
PLC
C
o
u
t n
r e
m
e
a
s
u
e r
1) An isolation transformer should be used.
2) An isolation transformer should be used.
Surge absorber
(FUJI Z-trap)
A
n
o
s i
e
t l i f
r e
s
h
o
u
d l
Twisted pair wires should be used between the noise
filter and power-supply terminals of the PLC.
Noise filter
Power
supply
Example: FUJI FHF-type
power filter
T
h
e
o f
o l l
w
n i
g
f
g i
u
e r
Other device
• The secondary side of the isolation transformer should
not be grounded as shown in the above ltem 1.
4-3
PLC
Electrostatic shielding
(to reduce the stray capacitance
between the primary and
secondary coils)
Device
Cabinet
b
e
u
s
e
. d
PLC
s
h
o
w
s
o
p
i t
m
u
m
n i
d
v i
d i
u
l a
Other device
PLC
Type D (Class 3) grounding
(ground resistance of
100Ω or less)
g
o r
u
n
d
. s
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