FIGURE 42 Progress in the reduction of core losses in silicon-steel and amorphous-alloy transformer materials. From Luborsky.77 Reprinted with permission.

three advances in magnetic alloys that not only constitute important scientific achievements but also are likely to have significant societal impact.

Reference was made to metallic glasses in the earlier section on rapid solidification processing. These amorphous materials, especially those based on iron-boron-silicon and iron-boron-silicon-carbon compositions in the metalloid content range of 15 to 25 atomic percent, display remarkably low magnetic hysteresis and eddy-current losses, mainly as a result of their high electrical resistivity and freedom from magnetocrystalline anisotropy as well as from grain boundaries and other microstructural defects. These materials in ribbon thicknesses have 60-Hz core losses that are less than a third of the best grain-oriented silicon steels, the latter embracing significant improvements in grain-growth and texture control over a period of 50 years. Still more recent research on metallic glasses has shown further reductions in core losses to approximately 1/20 that of the silicon steels. These advances are summarized in Figure 42.77

The implications of these metallurgical developments are great. It is estimated that core losses in distribution transformers alone amount to about $0.74 billion annually in the United States, and that a third of this waste could be saved if amorphous alloy cores were used instead of the present materials.77 A program is now under way to design and build one thousand 25-kVA distribution transformers for testing in service. Twenty-five of these transformers have already been constructed and are operating in various distribution systems. The test results thus far are in accordance with predictions, and the decision has been made to go ahead with production.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement