The construction of a dry-type transformer mainly consists of four core components: iron core, winding, insulation system, and cooling & structural parts, with the insulation system designed for air cooling (no insulating oil) as its most distinctive feature.

　　1. Core: Magnetic Circuit Core

　　The core is the path for magnetic flux and the foundation of the transformer’s electromagnetic conversion.

　　Material: High-quality cold-rolled silicon steel sheets (usually 0.3mm or 0.35mm thick). These sheets have low magnetic hysteresis loss, which reduces core loss during operation.

　　Structure: Stacked from silicon steel sheets cut into "E" and "I" shapes (or "Step-Lap" stepped shapes). The sheets are coated with an insulating film to prevent eddy current loss between layers.

　　Key Requirement: Tightly clamped with steel plates and bolts to ensure structural stability, avoid vibration noise, and maintain the integrity of the magnetic circuit.

　　2. Winding: Electrical Circuit Core

　　The winding is the conductor that carries current and realizes voltage transformation, divided into high-voltage and low-voltage windings.

　　Conductor Material: Copper wires (most common, with low resistivity and good heat resistance) or aluminum wires (cost-effective, used in some medium-and-low-capacity transformers).

　　Winding Form:

　　Layer winding: Conductors are wound in layers along the core column, suitable for low-voltage, large-current windings (e.g., low-voltage windings of distribution transformers).

　　Disc winding: Conductors are wound into circular discs, then stacked and connected in series, suitable for high-voltage, small-current windings (e.g., high-voltage windings of power transformers).

　　Insulation Treatment: Windings are wrapped with insulating materials (such as glass fiber tape, insulating paper) between turns and layers to prevent short circuits.

　　3. Insulation System: Core Guarantee for Dry Operation

　　Since dry-type transformers use air as the cooling medium (instead of insulating oil), the insulation system must be highly reliable to resist moisture, dust, and partial discharge.

　　Main Insulation: Insulates between high-voltage winding and low-voltage winding, and between windings and iron core. It usually uses glass fiber reinforced plastic (FRP) partitions or insulating paper tubes.

　　Turn-to-Turn/Layer-to-Layer Insulation: Insulates between adjacent turns or layers of the winding, using thin insulating paper (e.g., aramid paper) or enameled wire insulation (for small-capacity transformers).

　　Insulation Class: Classified by heat resistance, common grades include F-class (maximum allowable temperature 155°C) and H-class (maximum allowable temperature 180°C), which determine the transformer’s long-term operating temperature limit.

　　4. Cooling & Structural Parts: Operation Support

　　These parts ensure the transformer operates stably, safely, and with low noise.

　　Cooling System:

　　Natural air cooling (AN): Relies on natural convection of air to dissipate heat, suitable for small-capacity transformers (usually ≤1000kVA).

　　Forced air cooling (AF): Equipped with axial fans to blow air through the winding and core, increasing heat dissipation capacity by 30%-50%, suitable for medium-and-large-capacity transformers.

　　Structural Parts:

　　Frame: Made of steel, used to fix the iron core, windings, and other components, ensuring overall structural strength.

　　Terminal Box: Installed on the side of the transformer, with high-voltage and low-voltage terminals inside for external cable connection, and equipped with insulating bushings to prevent electric leakage.

　　Protection Cover: A metal or non-metallic shell that protects internal components from dust, moisture, and external impact; some covers have ventilation holes to facilitate air circulation.

　　Temperature Monitoring Device: Equipped with temperature sensors (e.g., PT100) to monitor the winding or core temperature in real time, and trigger alarms or trips when the temperature exceeds the limit.

　　If you need to understand the structural differences between specific types of dry-type transformers (e.g., cast-resin dry-type transformers vs. open-type dry-type transformers), do you want me to sort out a structural comparison table for these two types?