SEW-EURODRIVE has supplied its MOVITRANS® Contactless Energy Transfer system to Sasol Wax, a major manufacturer of a comprehensive range of mineral-oil based and synthetic paraffin waxes, petroleum jellies, and liquid paraffins, using a proprietary gas-to-liquid (GTL) process.
Sasol Wax produces a range of hard and medium waxes, all with different product codes, colours, hardness, and other special properties. As soon as a pallet is loaded, it is conveyed towards the aligned transfer trolley. The pallet then moves across to align with the exit conveyor, which takes it to the pallet-wrapping machine.
The two transverse trolleys each service conveyor lines from one of the packing robots, which were powered traditionally by drag chains in the centre of the rails. The transverse pallet trolleys each have two motors, one to drive the conveyor rollers, and the other to move the trolley along the rails.
These were powered traditionally via a drag chain that carried the power and communication cables. This was not an ideal solution, as the chain links would become clogged with wax, impeding their free movement. Operators were required to step into the cell when this happened to align the trolleys properly, often stepping on the chain inadvertently and causing it to break, resulting in costly downtime for repair or replacement.
This is where the MOVITRANS® Contactless Energy Transfer system from SEW-EURODRIVE provided an ideal solution, comments National Sales Manager, Norman Maleka. The system is based on the principle of inductive energy transfer, whereby electrical energy is transferred without contact from a fixed conductor. The electromagnetic connection required is made via an air gap, which means it is not subject to wear, making it maintenance-free and therefore much more cost-effective. Another important advantage of this type of power supply is that it is emission-free, and therefore environment-friendly.
SEW-EURODRIVE installed its MOVITRANS® Contactless Energy Transfer system in two phases, commencing with the instrumentation and communication side. A wireless PROFIBUS system (Process Field Bus) was installed to send control signals to the moving trolleys to avoid the need for communication cables in the drag chain. PROFIBUS is a standard for fieldbus communication in automation technology, championed initially in 1989 by BMBF (the German Department of Education and Research), and later deployed by Siemens.
In addition, a laser-based direct line-of-sight optical system was adopted to send signals to the moving trolleys. At the same time, the trolleys were modified to operate off SEW-EURODRIVE’s MOVIMOT® gearmotor drives. This is a compact modular VSD-driven system that uses the PROFIBUS-compatible MOVILINK® protocol for serial communication.
A line-cable loop was installed on the floor of the wax plant, covered by installation plates between the rails of the transverse trolleys to avoid cutting a groove on the concrete floor. This resulted in a quick and easy installation process that was both efficient and cost-effective, with no moving parts that could be damaged.
Two pick-up plates under each trolley transfer the electrical power to the MOVIMOT® gearmotor drives. Energy-transfer efficiency is enhanced by generating medium-frequency ac current. Three-phase mains power is converted into 25 kHz single-phase supply, which passes through the inductive loop on the floor. This induces a flow of ac current in the pick-ups under each trolley. The ac supply is rectified again on the trolley, and converted before being passed into the MOVIMOT® inverters for use by the motors.
“MOVITRANS® is the ideal power-supply system for any mobile application, such as when the equipment in question has to cover long distances, or where there is a particular requirement for a high-speed, maintenance-free energy transfer,” Maleka comments. Applications include conveyor trolleys, transport systems in logistics centres, linear-motion platforms with elevating tables or battery-charging supply units, overhead trolley systems, floor conveyors such as Automated Guided Vehicles, and storage and retrieval systems.