Transformer core classification
Commonly used transformer cores are generally made of silicon steel sheets. Silicon steel is a kind of steel containing silicon (silicon is also called silicon), and its silicon content is 0.8 to 4.8%. Silicon steel is used as the iron core of the transformer because silicon steel itself is a magnetic substance with strong magnetic permeability. In the energized coil, it can generate a large magnetic induction intensity, thereby reducing the volume of the transformer. The iron core is mainly composed of the iron core body, fasteners and insulating parts:
①The iron core body and magnetic conductor are made of electrical steel sheet.
②Fasteners, clips, screws, glass straps, rigid straps and pads, etc.
③Insulation parts, clip insulation, insulation tubes and insulation pads, grounding sheets and pads, etc.
The transformer core can be divided into
(1) Shell-type and core-type iron cores: The part of the iron core with the winding in it is called the 'core column', and the part without the winding that only acts as a magnetic circuit is called the 'iron yoke'. Where the iron core surrounds the winding, it is called the shell type; where the winding surrounds the core column, it is called the core type. The shell type and the core type have their own characteristics, but the manufacturing process of the transformer determined by the iron core is quite different. Once a certain structure is selected, it is difficult to switch to another structure. Most of the transformer cores in our country adopt the stacked core type.
(2) Single-phase and three-phase iron cores: Single-phase iron cores have single-phase two-column stacked iron cores. There are five types of single-phase single-column side-yoke four-column cores, single-phase double-column stacked cores, and single-phase radial stacked cores; three-phase cores include three-phase post-yoke stacked cores and three-phase side-yoke five-column cores. There are four types of iron cores, three-phase double-frame stacked iron cores, and three-phase reactor stacked iron cores.
(3) Three-dimensional and planar: the three-dimensional core and the iron yoke are not in the same plane, there are radial, involute, and symmetrical types, because the magnetic flux distribution is relatively uniform, which can reduce losses; the planar core In the same plane as the iron yoke, it has high mechanical strength and good workmanship.
(4) Stacked iron core and coiled iron core: Generally, they are stacked iron cores, which are made of stacked iron cores. There are many forms of coiled iron core. The air gap between the core column and the iron yoke of the involute iron core is large, which affects the no-load current, so the capacity cannot be made too small; but because the leakage flux enters the plane of the iron chip vertically and affects the additional loss, the sheet width is not suitable Too large, that is, the capacity cannot be too large.