Design and performance of permanent-magnet DC linear motors

Energy-efficient direct linear electric drives are gaining increased attention as a result of continuous developments in high-energy permanent magnets and advances in power electronics and microcontrollers. This paper presents a step-by-step approach to the design of permanent-magnet dc linear motors (PMDCLMs). The problems of armature reaction and saturation of the permeable members of the motor lead to a nonlinear and asymmetric air-gap magnetic flux density as a function of position and, consequently, the static thrust versus position characteristics of PMDCLMs. The paper describes a prototype PMDCLM that reveals these phenomena and presents design concepts aimed at alleviating these problems