Linear induction motors for low-speed and standstill application

Devices which are required to produce force with virtually no movement have zero power output. The effectiveness of such devices cannot therefore be assessed in terms of their efficiency or power/weight ratio. Quantities which are important in the design of force-producing machines or `actuators¿ are the force/input, force/weight and force/cost ratios and similar quantities. Reliability is also often a potent factor. The paper examines the use of linear motors as actuators under these criteria and formulates design procedure. The optimisation of the force/input ratio for a machine whose speed is not zero, but low in comparison to that of conventional machines, is carried out with the aid of a computer program. Considerable simplification of manufacture is achieved by the use of the tubular or axial-flux form of construction. Forces in linear motors of both transverse and axial-flux types are calculated, taking end effects into account. The design of an existing commercially produced tubular actuator is discussed.