An amorphous metal transformer (AMT) or amorphous core transformer is a type of energy efficient transformer found on electric grids.Kennedy, Barry (1998), Energy Efficient Transformers, McGraw-Hill The magnetic core of this transformer is made with a ferromagnetic amorphous metal. The typical material (Metglas) is an alloy of iron with boron, silicon, and phosphorus in the form of thin (e.g. 15-25 μm) foil rapidly cooled from melt. These materials have high magnetic susceptibility, very low coercivity and high electrical resistance. The high resistance and thin foils lead to low eddy currents losses when subjected to alternating magnetic fields. On the downside amorphous alloys have a lower saturation induction and often a higher magnetostriction compared to conventional crystalline iron-silicon, grain oriented electrical steel.K.Inagaki, M. Kuwabara et al., Hitachi Review 60(2011) no. 5 pp250, http://www.hitachi.com/rev/archive/2011/__icsFiles/afieldfile/2011/09/06/2011_05_113.pdf
Transformer low and high load losses At a constant power rating, AMTs are more efficient at both low and high loads, though AMT's require a larger core, due to the amorphous material's lower saturation induction and higher magnetostriction, and increased winding material resulting in a larger transformer size and weight .
No-Load or Low Load In a transformer the no-load or low load loss is dominated by the core loss. With an amorphous core, no/low-load core loss can be 70–80% lower than with traditional crystalline materials.
High Load In a transformer the high load loss is dominated by copper winding resistance, thus called copper loss. At high loads the lower saturation magnetization of both amorphous and electrical steel cores tend to result in a increasing lower efficiency as the transformer approaches full load. To minimise heavy load loss more copper and core material are necessary at a consequence of transformer increased size and weight.
Cost In 2026 when considering the same power rating, an AMT costs more than a traditional transformer due to expensive:
amorphous core material fragile handling requirements of the core material (Metglas) increased copper winding to compensate for core material's higher magnetorestriction
Applications The main application of AMTs are the grid distribution transformers rated at about 50–1000 kVA. These transformers typically run 24 hours a day and at a low load factor (average load divided by nominal load). The no load loss of these transformers makes up a significant part of the loss of the whole distribution net.
Amorphous iron is also used in specialized electric motors that operate at high frequencies of perhaps 350 Hz or more.
Advantages and disadvantages More efficient transformers lead to a reduction of generation requirement and, when using electric power generated from fossil fuels, less CO2 emissions. This technology has been widely adopted by large developing countries such as China"SPC Note on T&D network loss reduction and energy saving plan" SPC Transportation and Energy Section, Document #123, 1997 (in Chinese). and IndiaB.S.K. Naidu, "Amorphous Metal Transformers—New Technology Developments", Keynote Speech, CBIP-AlliedSignal Seminar (India), April 1999.. AMT are in fact more labour-intensive to manufacture than conventional distribution transformers, a reason that could explains a very low adoption in the comparable (by size) European market. These two countries can potentially save 25–30 TWh electricity annually, eliminate 6-8 GW generation investment, and reduce 20–30 million tons of CO2 emission by fully utilizing this technology.Li, Jerry (2011), Review and The Future of Amorphous Metal Transformers in Asia - a brief industry update, AEPN. Available at Researchgate or the author's personal page
Notes and references
External links Amorphous Metal Transformer Information Website Amorphous Metals in Electric-Power Distribution Applications Amorphous Ribbon for Transformers