Talking about the iron core in the transformer
The iron core is basically the same as the power transformer, and is composed of a core lamination, an insulating member and a core structure. The core body is composed of a magnetic steel strip with a high magnetic permeability. In order for different windings to induce a voltage proportional to the number of turns, the magnetic flux of the two windings is required to be equal, which requires a magnetic permeability in the winding. The core made of high material, try to make all the magnetic flux in the core and the two windings, and make the flux with only one winding chain as little as possible.
In order to reduce the excitation current, the core is made into a closed magnetic circuit, and the core is a skeleton for mounting the coil, which is an extremely important component for the electromagnetic performance, mechanical strength and transformer noise of the transformer.
The iron core laminated piece is formed by stacking or winding an electric magnetic steel belt, and the iron core structural part is mainly composed of a clamping piece, a footing, a gusset, a drawing belt, a pulling screw and a pressing nail. The structural members ensure sufficient clamping of the laminations to form a complete and strong core structure. There are insulating members between the laminations and the clips, the feet, the strut, the drawstring and the pull plate. The core lamination leads to the grounding lead to the clamp or to the external ground through the mailbox, and the iron core is not allowed to be grounded at multiple points. The lower clamp of the large transformer core is positioned by the positioning pin of the mailbox, and the positioning part of the upper part of the iron core is matched with the mailbox.
In order to reduce the no-load loss and no-load current of the transformer, the core is made of a cold-rolled electrical steel strip with a high magnetic grain orientation. In addition, a series of measures are adopted in the structure, and the core is lash-bonded without a hole. In order to adapt to the directionality of the cold-rolled oriented magnetic steel sheet and the core structure using magnetic circuit symmetry.
The portion of the core covered by the winding becomes a core post, and the other portion that is not surrounded by the winding to form a closed path of the magnetic flux becomes an iron yoke. The space defined by the iron core and the iron yoke is the core window, and the size of the core window is related to the number and cross-sectional area of the winding.
Transformer cores are generally divided into two categories, namely shell cores and core cores. Each type of iron core is divided into two types: a stacked iron core and a rolled iron core. The laminated iron core is formed by laminating the sheet-like electrical steel strips one by one; the rolled iron core is continuously wound by a suitable shape mold of the strip material on the winder. In addition, there is a double-frame iron core, that is, a large-size frame structure. However, since high-quality cold-rolled electrical magnetic steel strips are used, the width of the steel strip can meet the requirements of the width of the stem and the iron yoke, so the double frame is rarely used. )core. In addition, there are new double-frame and multi-frame structures, such as single-phase double-frame and three-phase four-frame structure.
According to the phase number of the transformer, the iron core of the single-phase transformer is collectively referred to as a single-phase iron core, and the iron core of the three-phase transformer is collectively referred to as a three-phase iron core; it can also be classified according to the number of columns of the transformer core, the number of frames, and the like.
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Single-phase transformer and three-phase transformer