From the perspective of raw materials, the fundamental difference between Dry-type transformers and Oil-immersed transformers lies in the different insulating media and winding encapsulation materials, which determines the composition of their entire material system.   Core insulation medium: oil or air + solid insulation Oil-immersed transformer Main insulation material: Mineral insulating oil (refined from petroleum fractions, such as naphthenic oil and paraffinic oil The insulating oil performs two main functions: electrical insulation and heat dissipation. The oil fills all gaps between windings, between windings and the core, and between windings and the tank. Dry-type transformers Main insulation material: Solid insulation system, no liquid insulation used Three common technical approaches: Epoxy resin casting type (mainstream): Windings are vacuum-cast and wrapped with epoxy resin Nomex paper insulation type (H-class Dry-type transformers): DuPont aromatic polyamide paper + air Glass fiber impregnation type: Glass fiber reinforced resin Heat dissipation relies entirely on air convection (AN) or forced fan blowing (AF)   Core Material: Basically the same Both cores use cold-rolled grain-oriented silicon steel sheets (CRGO), processed by stacking or winding. There is no fundamental difference in this raw material. Some high-end Dry-type transformers use amorphous alloy cores to reduce no-load losses, but this is not a dividing line between product categories.   Differences in materials between fuel tank and structural components Oil-immersed transformer Oil tank: Welded steel plate, inner surface coated with insulating varnish Accessories: Oil conservator, radiator/cooling pipes, gas relay, explosion-proof pipe, desiccant (silicone filter), oil filter valve These components are themselves important raw material components. Dry-type transformer Enclosure: Protective enclosure made of aluminum alloy or steel plate (IP20/IP23), no oil tank No oil conservator, no radiator, no gas relay Only a temperature control system (PT100 sensor + temperature controller) and cooling fan (optional) Overall material usage is significantly less than that of oil-fired transformers   Oil-fired transformers rely on "oil" for insulation and heat dissipation, so the windings can be bare and the oil tank must be thick and heavy; dry-fired transformers rely on "epoxy resin sealing" for insulation and "air" for heat dissipation, so the overall materials are lighter and cleaner, but the cost of epoxy materials themselves is not low.