Master redundancy
The AC 800M controller is linked to the PROFIBUS master Module CI854A. When a CI854A module fails or bus communication is interrupted, the redundancy partner is automatically activated. A CI854A pair balances the data cyclically over a fast link.
Line Redundancy
Line redundancy requires a redundant transmission medium and a redundant bus connection on the PROFIBUS master. The two transmission media are electrical cables in the simplest case, or fiber optical cables for higher requirements. For optimal usage of line redundancy, master/slaves/links with two bus terminals are required.
NOTE: The ABB Profibus Master Module CI854A has a build in line redundancy. For slaves with only a single PROFIBUS DP interface, the Redundancy link Module RLM 01 can be used to integrate the device in the redundant line structure.
The master, slave or link detects the failure of a line and continues communication over the intact redundant line. The requirements for line redundancy involve immunity to open circuit, short circuit and error adaptation in respect of cables, connectors, repeaters, media converters and links.
If the PROFIBUS slave has not been implemented a redundant PROFIBUS interface, and if, however, an analysis of the system availability shows the necessity of redundant PROFIBUS cabling, it is recommended to use a Redundancy Link Module RLM 01.
Slave redundancy
Slave redundancy refers to a situation in which at least redundant links/gateways and optionally redundant I/O modules are present. If a gateway module fails or a disturbance in communication occurs, the second gateway module takes over the task. The same principle applies to the I/O modules. The redundant module continues to record and/or output measured values in the case of an error. The connected sensors or actuators including the signal and command lines are generally
only set singly.
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