Intermediate Maintenance Electrician Technology

Author: Editor-in-Chief: Bian Meng
Publisher:
Publish Date: 2001-07-01
Features:
Fragment: Welding machine training requires understanding the basic structure and maintenance of power transformers, as well as the use and repair of welding machines and transformers. Section Power Transformer I. Structure of Medium and Small Power Transformers
A transformer is an electrical device that utilizes the principle of electromagnetic induction to convert one value of alternating voltage into one or more other alternating voltages of the same frequency. The electromagnetic induction in a transformer is achieved through two parts: the electrical circuit and the magnetic circuit. These two parts are interconnected; the current links with the magnetic flux, and the magnetic flux links with the current. The circuit is divided into the primary circuit and the secondary circuit. The main magnetic flux involved in electromagnetic induction links with both the primary circuit and the secondary circuit. Due to differences in the form, capacity, voltage, and windings of transformers, their external appearances and accessories may vary, but their main components are generally similar. In power transformers, the most commonly used are medium-capacity three-phase oil-immersed transformers with ratings between 100 and 800 kVA and voltages between 0.4 and 35 kV. These oil-immersed transformers are typically composed of the core assembly, tank, oil conservator, cooling, protection, and lead parts. The core assembly is the main part of the transformer, consisting of the core, windings, leads, and tap changer, with the core and windings being the two key components of the core assembly.
1. Core
The core is one of the most basic components of a transformer, with both the primary and secondary windings wound around it. Although the primary and secondary windings are not directly connected, when one winding is connected to a power source, due to electromagnetic induction, the other winding also induces an electromotive force. The core is used to conduct magnetic flux, which we call the magnetic circuit. Electromagnetic induction causes the core to generate currents called "eddy currents." The flow of eddy currents within the core generates heat, which can severely damage the transformer if it becomes excessive. To reduce the heat generated by eddy currents, the cores of transformers are made of stacked silicon steel sheets with thicknesses of 0.35 to 0.5 mm, as silicon steel sheets have excellent magnetic conductivity. To further minimize the heat caused by eddy currents, an insulating paint is applied to each layer of silicon steel sheet. This restricts the eddy currents to individual sheets, significantly reducing their magnitude.