YOKOGAWA FA-M3V e-RT3 Plus, Руководство по оборудованию

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A3-14
IM 34M06C11-01E
A3.3.3 Relay Circuits
The input/output points of the FA-M3 are normally connected directly to external
devices. Relays, however, should be placed between the input/output points of the
controller and the external devices in the following cases:
- The controller is far away from the external devices and is susceptible to noise
interferences in the field.
- The controller is to be connected to devices that will generate high-voltage noise.
- There is a need to clarify the relationship between other control lines with regards to
the responsibility of handling respective signals.
- A manually operated circuit needs to be included as a backup against failure of the
I/O equipment.
Sensor
r1 R1
IN
COM
DC input module
Relay
FA-M3
FA030303.VSD
Figure A3.11 Example of Use of Relay
A3.3.4 Protection against Output Short-circuit
If any of the loads connected to the output terminals of the FA-M3 are short-circuited, an
excess short-circuit current flows and there is the possibility that the external wiring will
burn or there will be a generation of abnormal heat. It is therefore common practice to
install fuses in the output circuits to ensure safety in the case of short-circuited loads
and minimize damage to the FA-M3. Use of external fuses is recommended, especially
for output modules that do not have built-in fuses or short-circuit protectors.
Figure A3.12 is an example of an FA-M3 that is equipped with output short-circuit
protection fuses. Note that these fuses are not intended to protect internal output
elements against possible damage. In addition, these fuses may fail to blow in failure
modes other than short-circuited loads.
FA-M3
Loads
L
L
L
L
L
L
L
L
Fuse
Fuse
Output module
Output points
Power supply to
output circuits
COM
FA030304.VSD
Figure A3.12 Example of Use of Output Short-circuit Protection Fuses