This is particularly the case with installations of multiple smaller drives, especially on conveyor applications in, for example, the food and beverage industries and materials handling.
In installations where multiple motors are spread around a facility such as bottling plants, food preparation and packaging plants and airport baggage handling installations, there may be dozens, perhaps hundreds, of drives, working together but spread over a large physical area.
In these cases cabling costs alone outweigh the cost of the individual drives and it makes sense to get the control closer to the motors.
The world´s first
The first electronic frequency converter developed 45 years ago – by Danfoss in Denmark – was essentially a decentral drive, suited to installation close to the motor it was driving.
These drives rapidly found favour in the food and beverage sector, on packaging machinery and conveyors, simply because it was impervious to the spillage of food or liquids and could easily be washed-down.
Some of these early VLT drives are still in operation today.
Back to the decentral idea
As technology moved forward with the rapid development of semi-conductor switching devices, the cooling need diminished and inverter drives were largely designed for installation in central control rooms, multiple inverters being installed in large control cubicles and cabled out to the drive motors, some very distant.
The wheel has come full circle and advanced technological development has led back to a high performance decentral format with all the control functionality and performance of larger central drives but now in an IP 66 enclosure especially designed to suit multimotor applications across a wide spectrum of industry.
Especially in food and beverage production areas, but also in pharmaceutical and cosmetic manufacturing plants, hygiene compliance rules in sensitive areas are extremely demanding.
In addition to the standards and guidelines of the EU, operators are increasingly observing the rules of the “European Hygienic Engineering & Design Group” – called EHEDG. The EHEDG provides the specifications and guidelines for the comprehensive, proactive protection of food from contamination with bacteria, fungi and yeasts during processing.
The result can be summarised under the heading “Hygienic Design”. Thus, the responsibility for implementing and achieving these targets lies with the machine manufacturers and operators. The hygienic design of process equipment and components should be based on a sound combination of process and mechanical engineering as well as knowledge in microbiology.
New hygienic trends
EU regulations for the compliance of hygienic equipment to be used in the manufacturing of popular food and beverages are becoming increasingly tight. For example, in the beverage industry, still water, fruit juices and alcohol free beers are all highly reactive to external influences.
New packaging materials also raise the demands on the hygienic conditions. Plastic packaging for cosmetics, including PET bottles in the drinks industry, require new measures as they do not tolerate heat sterilization or cleaning that previously rendered glass containers aseptic.
Today adopting hygienic requirements at the initial stage in the development of frequency drives is important, because upgrading of existing process equipment designs to meet the stringent hygienic requirements is often both expensive and unsuccessful. A good example of hygienic design is the EHEDG certified VLT Decentral Drive FCD 302 developed by Danfoss.