Lemminkäinen Infra Oy

For use in asphalt production and beyond

Inverter drives for harsh operating conditions

Inverter drives play an essential role in modern automation technology. This means that their capabilities are continually put to the test, often under difficult conditions. After all, unplanned downtime is not tolerable in virtually any production plant. This is just as true for mining, steel or cement production as it is for paper manufacturing, the automobile industry, the chemical industry or packaging technology. Numerous industrial sectors require inverter drives that not only offer functionality specific to the application, but also guarantee excellent reliability under difficult operating conditions and help to ensure reliable functioning of the entire plant. One company with such requirements is Lemminkäinen Infra Oy, Finland’s largest construction company.

Lemminkäinen Infra Oy is Finland’s largest construction company and a significant player throughout the Baltic region. Its activities include not only the construction and maintenance of road and rail networks, but also the production of the required raw materials. Between 2008 and 2009, for example, a state-of-the-art asphalt factory was built in Tuusula, Finland. It is now one of the three largest production facilities in Europe and produces approximately 500,000 tonnes of asphalt every year. The production volume per hour can reach up to 700 tonnes. Producing the required asphalt mixture – a combination of the bonding agent bitumen and various aggregates that must be adjusted for each individual application – is no easy task. Countless parameters must be considered in order to ensure, among other things, that the load capacity is suitable for the intended use of the final product. The basic production process, however, is easy enough to understand.

Drying, weighing, transporting, mixing

Reliable, convenient and practical

If the inverters need to be replaced, this can also be done without difficulty. While it is unlikely that the units will cause problems since they are designed to operate continuously for ten years (at 80% rated output), a replacement unit can be quickly installed in the unlikely case that this becomes necessary. This is made possible by the screwless removable control terminal and an integrated parameter backup. Data sets can therefore be quickly transferred to the new inverter, which leads to minimal downtimes. It does not stop there, however: the inverter drives used in Tuusula also have several further advantages which make them attractive for many other areas of application.
Both series of inverters are extremely compact in design and can therefore be installed “side by side” if needed, which of course saves installation space. Yet despite their comparatively small frame size, they achieve remarkable results: In heavy-duty mode, they can handle overloads of up to 150%. For applications that only require low overloads, the drive can be operated in normal-duty mode with up to 120% overload. This allows a smaller inverter drive to perform work that would normally require a larger drive. For controlled operation, the user can select between open-loop vector or V/f control.
With regards to communication capabilities, the inverters once again leave nothing to be desired since all conventional bus systems can be used to connect the inverters to a higher-level control network. The drive technology can therefore be incorporated into the user’s automation environment seamlessly. This opens up interesting possibilities in the areas of mechanical and plant engineering.