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What are Amorphous Core Transformers (AMT’s)?
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What are Amorphous Core Transformers (AMT’s)?
The cores of conventional transformers consist of stacks of laminations that are made from silicon steel with an almost uniform crystalline structure (CRGO). In transformers with amorphous cores, a ribbon of steel is wound to form the core. The big benefit of amorphous transformers is that amorphous steel has lower hysteresis losses. Simply put this means that less energy is wasted as heat during magnetisation and de-magnetisation of the core (see IR imagery below).Get more news about Amorphous core,you can vist our website!
Amorphous metals are made of alloys that have no atomic order. They are made by rapid cooling of molten metals that prevents crystallisation and leaves a vitrified structure in the form of thin strips. Due to the lack of systematic structure, this type of metal has also been given the name “The Metallic Glasses”.
This constitutes the major limitation of using Amorphous Core Transformers – and has limited the use of these types of transformers to low outputs and single phase devices below 250kVA.
TRUTH: To evaluate the short circuit withstand capacity of amorphous metal transformers, we have conducted a short circuit test on a 35/0.4kV transformer. It has passed the SC test successfully and the design is established and validated. For transformers of ratings above 250kVA we use foil for the LV windings. Usage of foil reduces axial forces and increases the short circuit withstand capacity of transformers. Radial forces are supported on the sides of the coil by a core pressing frame arrangement and solid phase to phase and phase to core insulation. We use epoxy diamond dotted (EDD) paper as inter layer insulation for LV & HV windings. EDD paper is made by applying heat curable resin in the form of square shaped dots on both sides of the kraft paper. The pattern of the resin dots ensures that there is sufficient space between them for oil impregnation. Windings made by this process are dried in the oven during which resin melts and cures. Through this process the layers are glued together and the complete winding becomes a solid block. The short circuit strength of such windings is considerably higher than that of conventional systems.
In silicon steel technology, the mother rolls are approx 1000mm wide and can be used to produce many varieties of widths of steel to optimise magnetic circuit designs and create designs to meet many varying customer standards. Amorphous steel sheets are currently only available in 3 widths which restricts design optimisation. Additionally, the number of world wide suppliers of Amorphous steel is extremely limited making the material price extremely volatile and unpredictable.
TRUTH: Even though the availability of amorphous material is limited to only three widths (142.2mm, 170.2mm and 213.4mm), by varying the number of core stacks and their thickness we can achive optimum transformer design. Since patent expiry of amorphous steel production there have beena number of additional suppliers and raw material prices are stable.