Fast components take the heat

Automated baggage sorters use actuators that consume only about a quarter of the energy required by alternative systems, while new motors have been developed for systems operating at up to 200°C and submerged in oil or vacuum. The actuators are linear motors, but linear synchronous motors (LSMs) as opposed to linear induction motors (LIMs). LSMs are not in themselves new – Hugh-Peter Kelly pioneered such actuators back in the 1980s. But Danish company Crisplant is the first to employ them in baggage and parcel sorting systems. The difference between LIMs and LSMs is that in an LIM, alternating current in an unrolled motor stator creates a moving magnetic field that induces currents in a typically aluminium reaction plate – the rotor in an ordinary motor. These currents interact with the moving stator field to produce thrust. In an LSM, on the other hand, the magnetic field is produced by permanent magnets. In the case of the Copley Motion Systems design, permanent magnets are placed in alternate orientations, end-to-end in a stainless steel tube. The tube with the magnets in it can be either the fixed or the moving part of the actuator. Crisplant has been using LIMs for high capacity sortation since 1990, but the company's LS-4000 series are the first to use LSMs. Models in the series are the LS-4000E tilt tray sorter, which can handle single tray items up to 1 x 1m and weighing 50kg, and the LS-4000CB cross belt sorter, which provides precise positioning and more gentle handling, making it suitable for high-friction and fragile items, especially in overnight delivery applications. According to Crisplant, the LS-4000E consumes an average of 2.4kW per hour while a comparable sorter using LIM technology consumes 10.3kW. The LS-4000CB similarly consumes 2.7kW, while a comparable LIM-powered machine requires 11kW. Applications include an LS-4000CB as part of an automatic tray handling system for Posten Norge's Østlandsterminalen mail centre near Oslo, and an LS-4000E sorter for TNT Pakketservice. Airport baggage handling applications include an LS-4000E tilt tray sorter and two LS-4000E sorters for Melbourne International Airport, scheduled to be operational in December 2010, and tilt tray sorters and a sort allocation computer for OR Tambo International Airport in Johannesburg, which was operational in time for the 2010 FIFA World Cup. More efficient than conventional motors and of increasing application to automation systems are brushless motors. These too use permanent magnets. Maxon Motor has just brought out a 22mm diameter 80W three phase brushless motor that can run in ambient temperatures of from -55 to 200°C, with internal components designed to withstand temperatures of at least 240°C. It is to be followed by 32mm and 42mm versions, plus a range of compatible gearheads. Applications include: gas turbine starter/generators for aircraft engines, regulation of combustion engines, oil and geothermal wells, robotic exploration vehicle systems, pumps and valves for liquid metal cooling systems and turbine fuel and steam and control, and valve adjustments for gas and steam power stations. The motors can be used in high vacuum, shock loaded and vibration applications to MIL-STD810F/Jan2000 Fig.514.5C-10 and submerged in oil.