The use of superconducting materials in many motors, machines, and power transmission lines has led to great increases in efficiency, reduction in the use of materials, and lower costs. The design of this machinery is dependent on certain physical properties unique to superconducting materials. One major area of engineering interest is the problem of energy dissipation in AC fields. After a brief description of material and machines, this book discusses the properties of "Type II Superconductors", as well as experimental techniques for measuring energy dissipation, surface conditions, surface barriers, temperature, and field dependence. A number of real systems are examined to illustrate practical applications.