Variable-speed drives (VSD) have increasingly become established in industrial plant engineering and even the consumer sector in recent years. In many cases, the reason for their selection can be found in total energy savings throughout service life. It is, for example, cheaper to have a variable-speed compressor supply precisely the flow of air required instead of running it at a fixed speed for maximum demand and generating the actual demand by means of throttles, and thus wasting energy. A further motivation frequently mentioned for the use of VSDs in industrial processes is the matching of actuator elements to diverse process requirements. Many of the advantages offered by VSDs in industrial applications can also be realized on the valve market and in electrical actuator drive systems, and new benefits are also being added. This overview article will: outline the structure and methods for "generation" of speed variation; explain the benefits using applications in the valve field; and indicate design and project-planning advantages arising from the use of VSDs.
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