Siemens ST PCS 7 manual Fault-tolerant automation systems, 10/15

© Siemens AG 2008

Automation systems

Fault-tolerant automation systems

■Overview ■Design

Fault-tolerant automation systems are used to reduce the risk of production failures. The higher investment costs for fault-tolerant automation systems are frequently negligible compared to the costs resulting from production failures. The higher the costs of

aproduction failure, the more worthwhile it is to use a fault-toler- ant system.

Fault-tolerant automation systems can be mounted in a UR2-H compact rack with divided backplane bus or in two separate racks (UR1 or UR2). The design in two racks allows physical separation of the redundant subsystems, e.g. by a fireproof par- tition.

Fault-tolerant automation systems can be used on their own in a plant configuration, or together with standard and safety-related automation systems.

Fault-tolerant automation systems for SIMATIC PCS 7 are avail- able as preassembled and tested all-in-one systems (AS bun- dles) at no extra charge.

Depending on the type of automation system, the RAM of these AS bundles varies as follows:

AS type Main memory

AS 412H 768 KB (512 KB for program and 256 KB for data)

AS 414H 2.8 MB (1.4 MB each for program and data)

AS 417H 30 MB (15 MB each for program and data)

Runtime licenses

Each AS bundle is already provided as standard with the SIMATIC PCS 7 AS Runtime license for 100 process objects (PO). The number of process objects can be extended by addi- tional Runtime licenses for 100, 1000 or 10000 POs. The process objects of additional Runtime licenses can be added to process objects which already exist. The number and type (e.g. 100 or 1000) of additional Runtime licenses are irrelevant. The AS Run- time licenses are administered on a SIMATIC PCS 7 engineering system or in the SIMATIC PCS 7 BOX.

Connection of process I/Os

Several PROFIBUS DP lines with distributed process I/Os can be operated on each sub-AS through the internal PROFIBUS DP in- terface or by using additional communications processors.

•The ET 200M remote I/O stations are connected via two IM 153-2 High Feature interface modules on a special bus module to two redundant PROFIBUS DP segments.

•The intelligent field devices on the PROFIBUS PA are con- nected over a DP/PA link to two redundant IM 153-2 High Feature interface modules.

•Non-redundant PROFIBUS DP devices, e.g. ET 200S distributed I/O devices, can be connected to the redundant

PROFIBUS DP over the Y-link.	10
These configurations can also be mixed together.

Communication over the plant bus

The AS 412H, AS 414H and AS 417H automation systems are connected as standard by one communications processor per sub-AS to the plant bus.

The plant bus can be implemented in the form of a ring structure, which can also be configured with redundant architecture if the availability requirements are high. When there are two redundant rings it makes sense to use two communications processors per sub-AS and to distribute their connections between the two rings (4-way connection). Double faults such as failure of the OSM/SCALANCE switch on ring 1 with simultaneous interruption in the bus cable on ring 2 can thus be tolerated.

Siemens ST PCS 7 · Update November 2008

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