High-density torque motor structures

Does electrical motor torque density depend on structural design? The aim of this paper is to provide a satisfactory reply to that question by comparing the torque density of several types of nonconventional motors with or without permanent magnets. It also addresses question of the use of specific materials; more precisely, whether the use of permanent magnets increases motor torque density, and if so, how such performance may be achieved, The practical limits of the torque density attained by each type of motor structure is also treated. The true capability of new designs, such as transverse flux motor structures, which have become popular in recent years, are discussed. New ways of investigating the design of high-density torque electrical motors, viable from both the industrial and economic points of view, are suggested.