1. Amorphous alloy material
   Amorphous alloy material is a new type of energy-saving material, which is mainly made of iron, nickel, cobalt, chromium, manganese and other metals as the alloy base, and a small amount of boron, carbon, silicon, phosphorus and other metal elements are added. It has Good ferromagnetism.

Amorphous alloy material adopts rapid rapid cooling and solidification production process. Its physical state is that the metal atoms are in a disordered amorphous arrangement. It is completely different from the crystal structure of silicon steel, which is more conducive to magnetization and demagnetization. The processed amorphous alloy core The thickness of the strip is only 0.025mm thick, and this new material is quite easy to use in the magnetization process of the transformer core. It can greatly reduce the no-load loss of the transformer. However, its flux saturation value is lower than that of traditional silicon steel materials (1.57T-1.59T), so the design flux density of amorphous alloy core is generally 1.3T-1.4T for single-phase transformers, and 1.25T-1.35 for three-phase transformers. A value between T is ideal.

Amorphous alloy core material is very sensitive to mechanical stress, whether it is tensile force or bending stress will affect its magnetic properties, so the core loss will increase with the increase of stress. This needs to be fully considered in the design of the body structure

2. Iron core structure

The amorphous alloy strip used in the amorphous alloy core has complex processing technology, hard and brittle material, difficult to cut, and difficult to deform and process. Therefore, the current strip specifications are only 142mm, 170mm, and 213mm in width, and the amorphous gold core can only be based on The capacity of the transformer needs to be made of strips of corresponding width to make a long rectangular section. From the structural point of view, the lower iron yoke is generally designed as an open single-roll core structure with staggered overlapping joints, so that it can be combined into a single-phase or Three-phase transformer core.

At present, the core structures of domestic three-phase amorphous alloy core transformers mainly include three-phase five-column (Figure 1) and three-phase planar wound core (Figure 2). Among them, the three-phase five-column type is more common. Usually, small distribution transformers with a capacity of 10KV and a capacity below 500KVA adopt a four-frame and five-column structure with four wound cores. When the capacity is large, it is limited by the width of the amorphous alloy strip. 8 wound cores are stacked together in two rows at the front and back to form a core structure with a large cross-sectional area. With this stacked structure, the capacity of a single amorphous alloy core transformer can reach 2500KVA.

In the design of amorphous transformers, the lamination coefficient of the amorphous strip core is generally in the range of 0.82-0.86, and the no-load loss process coefficient is generally about 1.4, which is more appropriate. The thickness coefficient of the superimposed part of the core opening is roughly 1.25 in China. And 1.18 two kinds. The specific selection of its value should be determined with the selected amorphous alloy core manufacturer before production.

3.Technical difficulties and corresponding process assurance measures for the production of amorphous alloy core transformers

1) Amorphous alloy core sheets are very sensitive to pressure, impact and bending. After being subjected to pressure, impact and bending, its no-load loss will increase, and at the same time, it is prone to breakage and slag drop, which may cause transformer insulation failure. Therefore, it is required to handle and put down gently during operation and handling to avoid impact and pressure. Especially for the staggered joints of the iron yoke opening, it must be carefully operated in the process of straightening and bending back to the original shape after the coil is assembled. At the same time, during the whole operation process, it is necessary to cover the upper end of the coil and insulation with clean cloth or insulating paper to prevent the powder produced by the core sheet from falling into the wire turns. In order to prevent the amorphous alloy sheet at the staggered seam of the lower yoke from falling fragments during the subsequent assembly process, before assembling the lower clamp and the insulation of the clamp, the metal fragments and dust must be sucked with a vacuum cleaner, and then the two parts of the joint should be cleaned. The sides are painted with insulating varnish for sealing treatment.
(2) Although the form of the amorphous alloy core can be regarded as a wound core, in order to fit the coil conveniently, the core manufacturer designs the lower yoke part as a form of multi-layer interlaced stacking with opposite seams. Why must the seam be arranged on the lower iron yoke, but not on the upper iron yoke?
As mentioned above, the lower yoke of the amorphous alloy core is detachable, that is, the amorphous wafer is a loose piece, which is easily damaged and cannot withstand pressure after assembly. After the transformer body is assembled, the whole body needs to be turned over 180°, so that collision and twisting cannot occur. The amorphous alloy core has to be in a suspended state after the transformer is assembled and in the future operation of the transformer. It is designed to avoid the phenomenon of increased loss or falling metal powder defects caused by the large stress of the amorphous alloy core. Therefore, this part is arranged below. Generally, products with smaller specifications can be turned over directly by a crane. It is very inconvenient to use a crane to turn over when the product specifications are larger, and a special turning table must be used to ensure the quality.
(3) Due to the unique pressure sensitivity of the amorphous alloy core, special requirements are put forward for the clamp structure, that is, the clamp is required to not only clamp the core, but also have a protective effect. Therefore, its clamp structure is rather special, completely different from S9 or S11 transformer clamps. In the design, it should be mainly ensured that insulating plates should be provided on both sides and top or lower part of the iron yoke, as well as on both sides of the side column for insulation, and steel plate clamping structural parts should be provided outside for protection. Corresponding measures should be reflected in the product design.