The primary challenge in this application was the delivery of accurate speed control from such large PM motors without the use of gearboxes. This involved the deployment of numerous feedback loops and in-depth commission routines.
The shredder application uses chains rotating within a chamber to not only crush and batter the waste/recycled material into pieces, but also to score and roughen its surface in order to increase its surface area. This increased surface area not only helps with drying, but also improves combustion when the output material is ultimately burnt to generate heat.
Herwig Reischl, CEO of AT Equipment and Services, explains the challenge: “Similar shredders use rotating knives to cut the waste material, but they do not modify the surface area, hence the use of chains in this instance. But chain-based systems present their own issues due to friction – frictional heat gains can actually cause the material to melt and clump together. It is for this reason that precise speed control is required, especially here with the lack of gearboxes, not only to make the shredding process as effective as possible, but also to prevent too much heat being generated by the constant abrasion. If the chain runs too slowly, we can also see issues with clumping and hooking.”