In terms of raw materials, what are the differences between Oil-immersed transformers and Dry-type transformers

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.