The choice of materials for the main transformer of a power transformer directly affects its efficiency, lifespan, and safety. It typically consists of three main categories: conductive materials, magnetic materials, and insulating materials.
Conductive Materials: The main transformer windings usually use high-purity electrolytic copper or aluminum. Copper conductors have better conductivity and higher mechanical strength, therefore they are more common in large-capacity or critical transformers; aluminum conductors are less expensive and lighter, and are also used in some small and medium-capacity equipment. The outer layer of the conductor is generally covered with insulating varnish or paper insulation material to prevent short circuits and partial discharges.
Magnetic Circuit: The iron core is usually made of cold-rolled grain-oriented silicon steel sheets laminated together. This material has high magnetic permeability and low loss characteristics, which can effectively reduce iron losses and improve transformer efficiency. The silicon steel sheets are isolated by an insulating coating to avoid the formation of eddy current loops, thereby reducing heat generation and improving operational stability.
Insulation and Auxiliary Materials: Main transformers widely use insulating paper, insulating oil (mineral oil or natural ester oil), epoxy resin, and other materials. In oil-immersed main transformers, transformer oil not only serves as insulation but also dissipates heat; insulating paper is used for insulation between windings and between layers; and the external structure mostly uses steel as the enclosure and supporting structure to ensure overall mechanical strength and short-circuit withstand capability.
