Lamination Materials

We have tried to assemble in one place both an overview of all the commonly used lamination materials, as well as some data which may be useful to designers of electromagnetic equipment.

Few decisions in the design of an electric motor are as fundamental, or have as far reaching consequences as the selection of the material to be used in the rotor or stator laminations. Motor output, heat rise, weight, and cost are only a few of the characteristics which are profoundly influenced by the selection of core material. ( The term motor is used loosely here to include generators, tachometers, resolvers, alternators, etc.) Unfortunately, few engineering schools take the time to explore in depth the practical aspects of this selection, and since the various materials come from a number of suppliers, it is difficult to find an overview of all the materials in one place. This article, while not intended to be exhaustive, should be helpful to motor designers trying to decide on the optimum material for their application.

The first point to make clear is that no one material is optimum (or even usable) for every application. As with all design decisions, trade offs must be made between cost, weight, size, and other factors. In addition, the processing of the laminations after fabrication can have a large influence on the performance of the unit being designed. The criteria for material selection include cost, permeability, core losses, and saturation flux density. Permeability and core losses vary with the frequency of flux reversals (in Hz), and with flux density. In certain applications, the shape of the hysteresis curve becomes important. Each of the available materials is optimized for one or more of these properties, while being less than perfect in other areas.