Physically Correct Measurement of Magnetic Energy Losses

Worldwide, hundred millions of generators, transformers and shunt reactors offer a continuous supply of electric energy. However, the majority exhibits excess energy losses, since machine cores are still manufactured from old-fashioned core material. Especially due to additional energy demands through electro-mobility, e.g. the EU requests a replacement of old, ineffective machines. As a handicap, no test principle is available for exact determinations of the materials energy losses. Two standardized tester types A and B show up to 10% difference of results. This impedes realistic energy assessments. World-wide, the reasons of differences are studied since 30 years. Recently, a theoretical study of the applicants revealed a significant source of error. It concerns the fact that - except for Japan - all testers lack from an indirect measurement of the most significant "magnetic field", rejecting so-called instable "tangential field coils". As a further problem, testers of type A magnetize a less than 1 kg weighing sample by a most expensive double-yoke of almost 500 kg mass. Whereas type B uses many sample strips of just 3 cm width. This is not realistic, and thus was recently withdrawn for standardized testing of high-class materials. This project aims on a systematic consideration of all above problems. A main point is to develop precise field coils of high stability by automatic, modern printing technologies (studied in a current FWF-project). For type A, this will allow for a "light yoke" of less than 100 kg mass. For type B, it will allow for just eight sample strips, however of three-fold width, for industrially relevant measurements. The above concepts promise two new versions of testers with identical, exact physical principle. This should yield strongly improved results. Testers A will become much lighter and cheaper through renouncement of a so-far needed hydraulic lift. Testers B will be directly representative for small machines, e.g. distribution transformers. Further, the new testers should offer broad affordability, including less-developed countries, small enterprises and academics. For them, so called "experimental windows" are planned, the tester serving as a magnetization tool for basic material investigations. In addition, the project also plans more correct measurements for already existing testers A and B. This should be attained by software corrections of field measurement, at least for comparison measurements. It is hoped that the novel concept yields distinctly improved results, of international acceptance. For this case, a final task of project is the preparation of a "Standardization Concept Paper", to initiate a later standardization of apparatus. A full compatibility with industrial demands is expected from close cooperations with two industrial partners, from Sweden and Austria.

An electric machine - like a generator, motor or transformer - needs a so called magnetic core, in order to distribute magnetic flux around the inner of machine, in optimized ways. However, as a specific problem, the core itself consumes magnetic energy that is entitled as "losses", in simple ways. Worldwide, these relatively minute losses exhibit extremely high relevance. A reduction of just one percent would be sufficient to supply a large city with electric energy. In a seemingly paradoxical way, the so far available test technologies do not offer exact loss measurements, being restricted to approximations. The reason sounds quite trival, while it shows high complexity in practice: So far testers fail to determine the "magnetic field strength". As an alternative, they determine the magnetization current, as a quantity that lacks exact proportionality. However, advanced, novel methodologies of manufacturing, like 3D printers, offer the production of field sensors with highest precision and sensitivity. In the course of project work, automatically manufactured components as well as clever theories were developed in order to create a "Physically Consistent Single Sheet Tester" (PC-SST). For the first time, it determines losses with high precision - avoiding all kinds of compromizes and standardization conventions. This justifies urgent claims to start a process of international standardization of PC-SST, which however may involve long years of word-wide discussion. As a very relevant feature, the applicability of so far loss testers was restricted to mains frequency, i.e. 50 Hz (or 60 Hz in some regions outside of Europe). On the other hand, the new technology can be applied for increased intensities of magnetization, and up to frequencies of several thousands of Hertz, as needed for novel fields of electro-mobility. Further, manufacturing is facilitated, and corresponding costs are strongly reduced. As a final result, the mass of apparatus is not of the large order of hundreds of kilograms any longer. In fact, the novel tester is rather light and compact, compared to existing standardized ones.