What does the structure of the transformer look like in a new energy vehicle?

Classification of transformers, in order to adapt to different purposes of use and working conditions, there are many types of transformers, and various types of transformers differ greatly in structure and performance. Several common transformers are shown in Figure 2-34.

In general, transformers can be classified according to their use, structure, number of phases, cooling method and cooling medium. According to the use, there are mainly power transformers, voltage regulators, instrument transformers, special purpose transformers, etc.

New energy vehicle drive motor technology, according to the number of phases, mainly includes single-phase transformers and three-phase transformers. According to the number of windings, there are mainly autotransformers, double-winding transformers and three-winding transformers, according to the different core structure, transformers can be divided into core transformers and shell transformers. According to the cooling medium and cooling mode, transformers can be divided into air-cooled dry-type transformers, oil-immersed transformers with oil as cooling medium and gas transformers with gas as cooling medium. 2. The structure of the transformerThe main components of the transformer are: core, winding, transformer oil, oil tank and accessories, insulating bushing. The iron core and winding are the main components of the transformer, called the body; As the shell of the transformer, the fuel tank plays the role of cooling, heat dissipation and protection; Flexor oil plays both the role of cooling and the role of insulating medium; Insulating bushings mainly play an insulating role. The main components of the transformer are briefly described below.

(1) Core material of transformer

1.) Iron core material. The iron core is the main magnetic circuit of the magnetic conduction in the transformer and is also the mechanical skeleton of the set winding. The core is made of soft magnetic materials with high permeability, hysteresis and eddy current losses. In the early stage of transformer development, ordinary iron sheets were used as core materials, and hot-rolled magnetic steel sheets were later developed as core materials. In 1934, Gauss invented cold-rolled grain-oriented silicon steel sheets, gradually replacing hot-rolled silicon steel sheets. In 1968, Nippon Steel Corporation of Japan first developed a high-permeability silicon steel sheet I-Hi-B grain-oriented silicon steel sheet, which has a unit loss and the number of excitation ampere turns are smaller than ordinary grain-oriented silicon steel sheets, so it is widely used. In the 80s of the 20th century, lower-loss silicon steel sheets with magnetic domain refinement (by laser irradiation or mechanical indentation) were introduced. The most important properties of silicon wafers are the loss per unit mass and the magnetic permeability of the material. The loss of cold-rolled grain-oriented silicon steel sheets is greatly reduced than that of hot-rolled silicon ortho-sheets, so at present, almost all power transformers use cold-rolled grain-oriented silicon steel sheets as core materials.

Non-grade alloy is another core material after cold-rolled grain-oriented silicon steel sheet, which is characterized by high magnetic permeability, no-load current and no-load loss are greatly reduced than that of oriented silicon steel sheet. In the mid-60s of the 20th century, foreign countries have begun to study amorphous materials, and in 1974 began to be applied to transformer cores, and CE Company in the United States was the first to manufacture 25kV with non-grade alloys. A transformer is now available at 2500kV· A's amorphous alloy core transformer. However, due to the low saturation flux density of non-grade alloys, the difficulty of processing thin thickness, and the high price of materials, it has not been widely used in the manufacture of large-capacity transformers.

At present, most of the transformer core is made of cold-rolled silicon steel sheets with a thickness of 0.15~035mm, and the silicon content in the silicon steel sheet is about 4%. The surface of silicon steel sheet is generally covered with an insulating film with high electrical insulation, and the insulating film has extremely high insulation resistance and good mechanical properties. According to statistics, the iron consumption of transformers in developed countries accounts for about 4% of the total power generation, so reducing the iron consumption of transformers is an important measure to improve the efficiency of the power grid. The reduction of iron consumption is mainly achieved by increasing the silicon content of silicon steel sheet and reducing the thickness of silicon steel sheet, and the thickness of silicon steel sheet is currently reduced from 0.35mm in the early stage to 023mm.18mmo at present

2.) Core structure. The iron core is composed of two parts: the iron core column and the iron core. Among them, the part of the core covered by the winding is called the core column, and the part connecting the core column to form a closed magnetic circuit is the magnetic or iron column, as shown in Figure 2-35. The core of modern transformers, the core column and iron body are generally in the same plane, that is, the planar core.

According to the different core structure, transformers are divided into core transformers and shell transformers. Figure 2-35 shows a core structure transformer whose core column is surrounded by windings. Single-phase and three-phase shell transformers are shown in Figure 2-36, which is a structure in which the iron core surrounds the top, bottom and sides of the winding.

The advantages of core transformers are that the circular coil is convenient to manufacture, the amount of silicon steel sheet is relatively small, and the winding arrangement and insulation are easier, so most power transformers adopt core structure; The disadvantage is that there are many specifications of iron core lamination, and the binding of iron core posts and clamping requirements of iron equipment are higher. The shell transformer structure has good mechanical strength, but the processing technology is special, the insulation structure is complex, the maintainability is poor, and the cost is high, and it is generally used in special transformers and small-capacity single-phase transformers.

For transformer products, it is common to connect a single or several coils that are connected according to the provisions and can change voltage and current as windings, such as primary winding, secondary winding.

The winding is the circuit part of the transformer and is an important part of the transformer. During the operation of the transformer, current passes through the windings, which will produce resistance loss, which will cause heat generation and reduce transformer efficiency, and may also encounter overvoltage and high temperature. Harsh conditions such as overcurrent. In order for transformers to operate safely and reliably over the long term, transformer windings must meet basic requirements such as electrical, mechanical and thermal requirements. The conductor materials of transformer windings are generally copper and aluminum with high conductivity, and the conductor shapes include round wires, flat wires and foil plates. Power transformers generally use flat copper wires, round copper wires are mainly used in small transformers and transformers, and foil plates are mainly used for capacity less than 2000kV· Small and medium-sized transformers below A. According to the different insulation materials, the conductor can be divided into paper-wrapped winding wire (referred to as paper-wrapped wire), enameled winding wire (referred to as enameled wire), wire-wrapped winding wire (referred to as wire-wrapped wire) and glass-coated winding wire (referred to as glass-coated wire).

The structure of the winding is related to the capacity of the winding, and the processing needs to be considered at the same time