The role of the effect of manufacturing tolerances on a tubular linear ferrite motor

Electric machines are often designed without considering workmanship and materials tolerances. Their manufacturing process involves a series of steps, starting with raw materials and ending with the machine assembly. In each of these steps occur deviations due, for instance, to mistakes in positioning tools or to the tolerances in the electrical and magnetic characteristics of the materials. These deviations may cause unwanted parasitic effects such as torque ripple, losses or acoustic noise. Such effects have to be considered especially in machines used in industrial drives for high performance applications. Moreover the tolerances in the magnetic materials have a considerable effect on the cogging torque value [1]. Many previous studies analyze the effects that these tolerances have on the rotating permanent-magnet synchronous motors performances [1-4], while this one focuses on the evaluation of the effects on the Tubular Linear Ferrite Motors (TLFM) performances. That is because the effects of such tolerances are considerably strong on linear machines as their asymmetrical geometry doesn't allow a cyclic behavior.