Redundancy; Basic Principles; Media Redundancy - Pepperl+Fuchs LB Series Manual

LB Remote I/O System
Installation
3.13

Redundancy

3.13.1

Basic Principles

Redundancy is used when it is necessary to guarantee operation of a remote I/O station
despite one or more components having failed.
To build a redundant system, use backplanes LB9022* and LB9029A and equip these with two
com units for com unit redundancy and three power supplies for power supply redundancy.
Two power supplies are sufficient to supply the entire backplane. The third power supply is a
redundant power supply that can compensate for the failure of another power supply.
It is possible to tell which com unit is active by looking at the operating mode LED. If the
operating mode LED is flashing, the com unit is active. If the operating mode LED is not lit, the
com unit is passive. For more information about the status LEDs, refer to the data sheet for the
relevant com unit in use.
As a general rule, a distinction is made between media redundancy and application
redundancy. Com units can be set to media redundancy or application redundancy using the
configuration software. For more information, refer to the software manual for the com unit
used.
Note!
Note that both com units in a redundant system must have the same firmware.
3.13.2

Media Redundancy

Media redundancy is when the master communicates with a com unit via a voter and a
redundant fieldbus cable. The com unit that communicates with the master is active and
controls the I/O module on the backplane. The second com unit is passive and reads the data
traffic on the backplane.
If the active com unit fails, the passive com unit automatically takes on the configuration of the
com unit that was previously active. When there is media redundancy, switching between the
com units is independent of the fieldbus cable used.
Master
Figure 3.14
If the master is also redundant, this is known as extended media redundancy.
Master
Red.
Master
Figure 3.15
Voter
Fieldbus
Redundant
Fieldbus
Line redundancy
Voter Fieldbus
Redundant
Fieldbus
Voter
Extended media redundancy
Backplane
Backplane
43