AC Mains Filters
The DL305 AC powered base power
supplies require extra mains filtering to
comply with the EMC Directive on
conducted RF emissions. All PLC
equipment has been tested with filters
from Schaffner, which reduce emissions
levels if the filters are properly grounded
(earth ground). A filter with a current
rating suitable to supply all PLC power
supplies and AC input modules should be
selected. We suggest the FN2080 for
DL305 systems.
NOTE:
Very few mains filters can reduce problem emissions to negligible levels. In some cases, filters may
increase conducted emissions if not properly matched to the problem emissions.
Suppression and Fusing
In order to comply with the fire risk requirements of the Low Voltage and Machinery
Directive electrical standards (EN 61010–1 and EN 60204–1), by limiting the power into
“unlimited” mains circuits with power leads reversed, it is necessary to fuse both AC and DC
supply inputs. You should also install a transient voltage suppressor across the power input
connections of the PLC. Choose a suppressor such as a metal oxide varistor, with a rating of
275VAC working voltage for 230V nominal supplies (150VAC working voltage for 115V
supplies) and high energy capacity (eg. 140 joules).
Transient suppressors must be protected by fuses and the capacity of the transient suppressor
must be greater than the blow characteristics of the fuses or circuit breakers to avoid a fire
risk. A recommended AC supply input arrangement for Koyo PLCs is to use twin 3 amp TT
fused terminals with fuse blown indication, such as DINnectors DN–F10L terminals, or twin
circuit breakers, wired to a Schaffner FN2010 filter or equivalent, with high energy transient
suppressor soldered directly across the output terminals of the filter. PLC system inputs
should also be protected from voltage impulses by deriving their power from the same fused,
filtered, and surge-suppressed supply.
Internal Enclosure Grounding
A heavy-duty star earth terminal block should be provided in every cubicle for the connection
of all earth ground straps, protective earth ground connections, mains filter earth ground
wires, and mechanical assembly earth ground connections. This should be installed to comply
with safety and EMC requirements, local standards, and the requirements found in IEC
1000–5–2.The Machinery Directive also requires that the common terminals of PLC input
modules, and common supply side of loads driven from PLC output modules should be
connected to the protective earth ground terminal.
DL205 Installation and I/O Manual, 2nd Edition
A-5
Appendix A: European Union Directives (CE)
A
2
3
A
5
H
7
10
A
10
11
12
13
14
A
B
C
D
Earth
Terminal
Fused
Terminals
Filter
Transient
Suppressor
To AC
Input
Circuitry
Schaffner
FN2010
L N
