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Introduction to the classification of power transformer core

2019-04-01 13:19:23

1. High frequency class: Iron powder core Ferrite core

Ferrite core is used in high-frequency transformers. It is a ceramic magnet with a spinel crystal structure. This spinel is iron oxide and other divalent metal compounds. For example, kFe2O4 (k stands for other metals), currently The metals used are manganese (Mn), zinc (Zn), nickel (Ni), magnesium (Ng), copper (Cu).

Its common combinations are manganese Zn (Mn Zn) series, nickel zinc (Ni Zn) series and magnesium zinc (Mg Zn) series. This material has high magnetic permeability and resistive physical properties, and its use frequency ranges from 1 kHz to over 200 kHz. .

2. Low frequency class: silicon steel sheet (LAMINATION)

Silicon steel sheets are used in low-frequency transformers. There are many types of them. According to their different manufacturing processes, they can be divided into A: calcined (black film) and N: no calcined (white film). According to their shapes, they can be divided into: EI type. , UI type, C type, mouth type.

Oral silicon steel sheet is often used in transformers with high power. It has good insulation performance, easy heat dissipation, and short magnetic circuit. It is mainly used for powers greater than 500~1000W and high power transformers. It consists of two C-type silicon steel sheets. The silicon steel sheet is called CD type silicon steel sheet. The power transformer core made of CD type silicon steel sheet has the same window, and the higher the window, the higher the window.

The larger the power transformer core is. The coils can be separately mounted on both sides of the core. Therefore, the number of turns of the transformer can be distributed on two wire packages, so that the average length of each wire package is shorter, and the copper consumption of the coil is reduced. Small. In addition, if the two coils that require symmetry are wound on two wire packages, a completely symmetrical effect can be achieved.

A set of silicon steel sheets consisting of four C-type silicon steel sheets is called ED type silicon steel sheet. The transformer made of ED type silicon steel sheet has a flat and wide shape. Under the same power, the ED type transformer is shorter than the CD type transformer, and the width is shorter. Larger, because the coil is installed in the middle of the silicon steel sheet, there is an external magnetic circuit, so the leakage magnetic is small, and the overall interference is small. However, all the coils are wound on one wire package, and the wire package is thick, so the average length is longer. , copper consumption is larger.

The C-type iron core has excellent performance, small size, light weight and high efficiency. From the perspective of assembly, the C-type silicon steel sheet has few parts and strong versatility, so the production efficiency is high, but the C-type silicon steel sheet processing process is better. More, more complex, the need to use special equipment to manufacture power transformer core, so the current cost is still higher.

E-type silicon steel sheet is also called shell or day-type silicon steel sheet. Its main advantage is that the primary and secondary coils have a common wire frame and have a high window duty factor (duty factor Km: net cross-sectional area and window of copper wire). Area ratio); silicon steel sheet forms a protective casing for the winding, so that the winding is not easily damaged by mechanical damage; at the same time, the heat dissipation area of ​​the silicon steel sheet is large, and the magnetic field of the transformer is less divergent. However, its primary and secondary leakage inductance is large, and the external magnetic field interference is also large. In addition, due to the long average circumference of the winding, the EI core transformer uses more copper wire under the same number of turns and core cross-sectional area.

The thickness of silicon steel sheets is usually 0.35mm and 0.5mm.

The assembly method of the silicon steel sheet has two methods: the overlap method and the overlap method. The overlap method is to alternately distribute the openings of the silicon steel sheets one by one on both sides. This stacking method is troublesome, but the gap between the silicon steel sheets is small and the magnetic resistance is small. It is beneficial to increase the magnetic flux, so the power transformer adopts this method. The stacking method is often used in the case where a direct current is applied, in order to avoid saturation caused by the direct current, there is a gap between the silicon steel sheets, so the stacking method will The E piece and the I piece are placed one on each side, and the gap between the two can be adjusted by the paper piece.

3.COIL class: divided into three types.

A.TOROID toroidal core: It is made of laminated O-shaped or wound from silicon steel sheet. This kind of iron core is very difficult for winding.

B.ROD CORE rod core.

C.DRUM CORE: drum core.