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xxix
Conformance to EC Directives
6
6-4
Relay Output Noise Reduction Methods
The CP1H PLCs conforms to the Common Emission Standards (EN61131-2)
of the EMC Directives. However, noise generated by relay output switching
may not satisfy these Standards. In such a case, a noise filter must be con-
nected to the load side or other appropriate countermeasures must be pro-
vided external to the PLC.
Countermeasures taken to satisfy the standards vary depending on the
devices on the load side, wiring, configuration of machines, etc. Following are
examples of countermeasures for reducing the generated noise.
Countermeasures
Countermeasures are not required if the frequency of load switching for the
whole system with the PLC included is less than 5 times per minute.
Countermeasures are required if the frequency of load switching for the whole
system with the PLC included is more than 5 times per minute.
Note
Refer to EN61131-2 for more details.
Countermeasure Examples
When switching an inductive load, connect an surge protector, diodes, etc., in
parallel with the load or contact as shown below.
Circuit
Current
Characteristic
Required element
AC
DC
Yes
Yes
If the load is a relay or solenoid, there is
a time lag between the moment the cir-
cuit is opened and the moment the load
is reset.
If the supply voltage is 24 or 48 V, insert
the surge protector in parallel with the
load. If the supply voltage is 100 to
200 V, insert the surge protector
between the contacts.
The capacitance of the capacitor must
be 1 to 0.5
µ
F per contact current of
1 A and resistance of the resistor must
be 0.5 to 1
Ω
per contact voltage of 1 V.
These values, however, vary with the
load and the characteristics of the
relay. Decide these values from experi-
ments, and take into consideration that
the capacitance suppresses spark dis-
charge when the contacts are sepa-
rated and the resistance limits the
current that flows into the load when
the circuit is closed again.
The dielectric strength of the capacitor
must be 200 to 300 V. If the circuit is an
AC circuit, use a capacitor with no
polarity.
CR method
Power
supply
Inductiv
e
load
C
R
Summary of Contents for CP1H-CPU - 05-2006
Page 2: ...CP1H X40D CP1H XA40D CP1H Y20DT D CP1H CPU Unit Operation Manual Revised May 2006...
Page 3: ...iv...
Page 11: ...xii TABLE OF CONTENTS...
Page 15: ...xvi...
Page 19: ...xx...
Page 31: ...xxxii Conformance to EC Directives 6...
Page 71: ...40 Function Blocks Section 1 5...
Page 133: ...102 Computing the Cycle Time Section 2 7...
Page 169: ...138 CPM1A Expansion I O Unit Wiring Section 3 6...
Page 411: ...380 Clock Section 6 8...
Page 519: ...488 Replacing User serviceable Parts Section 10 2...
Page 527: ...496 Standard Models Appendix A...
Page 535: ...504 Dimensions Diagrams Appendix B...
Page 628: ...597 Connections to Serial Communications Option Boards Appendix F Connecting to Unit...
Page 629: ...598 Connections to Serial Communications Option Boards Appendix F...
Page 659: ...628 PLC Setup Appendix G...
Page 665: ...634 Index work words 159 write protection 370...
Page 667: ...636 Revision History...