Siemens SIMATIC PCS 7 Function Manual page 37

Mounting racks
The following three racks are available for installing the S7-400H. Normally, the UR2-H rack
is used.
Module type
UR2-H
UR1
UR2
Central processing units
There are two CPUs in an H-system. The two CPUs are connected to one another using
synchronization modules and fiber-optic cables.
Power supply
A separate power supply module from the standard S7-400 series is needed for each
subsystem of the S7-400H. Two power supply modules can be used in each subsystem to
increase the availability of the fault-tolerant system. In this case, use the following power supply
modules that can be used for redundancy.
Power supply modules for 24 VDC as well as for 120/230 VAC nominal input voltages with
output currents of 10 and 20 A.
Synchronization modules
Synchronization modules are used to link the two central processing units. They are installed
in the central processing units and interconnected with fiber-optic cable. Two synchronization
modules are installed in each CPU.
Set the rack number for the H CPU as of firmware version V4.X directly on the CPU. The
synchronization modules can be replaced in runtime.
The same rack number must be set at all synchronization modules up to firmware V3.x.
Fiber-optic cables for synchronization
The fiber-optic cables are connected to the synchronization modules and form the physical
connection (redundancy link) between the two automation stations. The synchronization
cables must not be cross-connected.
In addition to the standard lengths of 1 m, 2 m, and 10 m, custom-made synchronization cables
are available in lengths up to 10 km.
Fault-tolerant Process Control Systems (V8.0)
Function Manual, 03/2012, A5E02779471-02
Size Special feature
2 x 9 slots Installation of two separate subsystems each with nine
modules. The two subsystems are electrically isolated
(not mechanically).
It is not possible to replace a rack in runtime.
1 x 18 slots Two racks are required for an S7-400H .
You can replace a rack in runtime.
1 x 9 slots Two racks are required for an S7-400H .
You can replace a rack in runtime.
Fault-tolerant Solutions in PCS 7
3.2 Solutions for automation systems
37