Russian AUTOMATED TRAFFIC CONTROL SYSTEMS home Services Projects Solutions Certificates Partners Vacancies Contacts Automated process control systems (APCS) Systems of increased reliability Siemens H-systems The redundant Siemens S7-400H system develops the concepts of building control systems with increased reliability, the foundations of which were implemented in the controllers of the SIMATIC S5 family. The reliability of the system is supported by the operating system and the hardware of the CPU 414-4H or CPU 417-4H. The basic principle of the Siemens S7-400H programmable controller is the principle of hot backup with support for bumpless automatic switching to the backup base unit in the event of a failure of the master base unit. According to this principle, in the absence of faults, both base units are active and synchronously execute the same program. Both blocks synchronously form control actions, but these actions are output through the output modules only from the master block. In the event of a failure, all control functions are taken over by a serviceable controller unit. Reliable high-speed communication is required for guaranteed bumpless switching of the reserve between the base units of the controller. This link is maintained over fiber optic cables connecting the two CPUs. Synchronization functions on these cables are performed automatically by the controller operating system and do not require user programming. The use of the S7-400H controller provides a number of advantages: - Transparent programming. Programs can be written in all languages available for the S7-400. A program written for a conventional CPU can be executed by the CPU of a redundant controller and vice versa. When writing a program, only the technological features of the control object are taken into account. The issues of increasing the reliability of the system functioning are solved by the operating system and the hardware of the controller. Additional software is only required to configure the redundant system. - Standard data processing. From the user's point of view, the S7-400H controller has only one CPU and one program. - Fast bumpless switchingfrom master to slave with a typical switching time of 30 ms. During the switchover period, the operating system eliminates the possibility of data loss or interrupt signals. - Automatic synchronization of central processors after replacing one of them. After replacing one of the central processors, it is envisaged to perform automatic bumpless synchronization with the transfer of all current data (programs, data blocks, dynamic data, etc.) to the memory of the processor included in the operation.