Plant Management
Selective measures are already taken today, in order to shut down plant sections during breaks. These are, however, very application-specific. Frequently the actual control task and the energy management are amalgamated. This all makes the program generation, but especially the maintenance of such software, very difficult.
Diagram 3. Initiation of shutdown by the user by sending the PROFIenergy command and transmission of the length of break. The local intelligence, using the example of a robot here, decides which units can be shut down, in order to remain ready for production on expiration of this period.
Non-productive periods
Whereas in operation the focus is on energy-saving products such as motors with a better energy efficiency class, PROFIenergy allows savings to be made predominantly during the non-productive periods. In this case, it is a matter of partially or completely switching off unnecessary systems. Users can expect energy savings of up to 80 per cent. A further key factor is the sensible deployment of the
energy available during production. Here, too, certain auxiliary processes can take a break during production. PROFIenergy thus has the task of managing and making most efficient use of the energy available. Partial load operation must be possible.
In addition, external hardware is necessary for the execution of the actual switching process and this hardware must be configured, installed and maintained. The cost of doing this often outweighs the actual savings,
so many users do not take such measures PROFIenergy also offers an economical solution here. This is a matter of a pure data interface, as the switching functions are already integrated in the devices. In addition, there is a clear separation between the program
sections for the energy management and the control logic. Both parts are clearly separated from one another and can be tested and put into service independently of one another.
Structured programming
Diagram 4. Calculation of the absolute moment at which the starting command is to be sent to the respective device, so that all devices are ready for operation again at the required time. To calculate this, the startup time previously reported by the individual devices is to be subtracted from the required target time.
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In the long term, the care and maintenance of the user program is significantly simpler due to structured programming. This enables users in turn to integrate PROFIenergy easily into their own (factory) standards and program libraries. l
Mark Freeman is Product Manager, Siemens Industry Automation & Drive Technologies, Manchester, UK.
http://www.industry.siemens.co.uk/home/uk/en/IADT/Pages/ Default.aspx
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