Dry Type Distribution Transformer Core Components Explained: A Comprehensive Breakdown from Core to Fan

In power distribution systems, drytype transformers have become the preferred choice for indoor applications such as commercial complexes, highrise buildings, data centers, subway stations, hospitals, and industrial plant electrical rooms – thanks to their outstanding advantages in fire safety, oilfree environmental protection, and maintenancefree operation.

However, when faced with a drytype transformer, most users can only see its rugged enclosure and neatly arranged terminals, with little awareness of the core components hidden inside – the parts that truly determine performance and service life.

The quality of a transformer is not in its casing, but in its inner craftsmanship.

This article takes Kaibeite drytype distribution transformers as an example to break down each internal core component – what they are called, what functions they perform, and why each one directly affects the equipment's operating performance over the next ten or even twenty years.

I. Iron Core – The Magnetic Flux Path, the "Heart" of the Transformer

The operating principle of a transformer is based on the law of electromagnetic induction. When AC current flows through the primary winding, an alternating magnetic flux is generated in the iron core, which induces a corresponding voltage in the secondary winding. The iron core is precisely the closed path for this magnetic flux, and its performance directly determines the transformer's noload losses, magnetizing current, and operating noise.

Kaibeite drytype transformers employ highpermeability coldrolled grainoriented silicon steel laminations, formed through a 45° fullmiter steplap stacking process. Highquality materials and precision manufacturing effectively reduce hysteresis losses and eddycurrent losses, enabling the transformer to maintain excellent operating conditions with low losses, low noise, and low temperature rise over the long term.

II. Windings – Current Carriers, the "Blood Vessels" of Energy Transmission

Internal HV Winding & Internal LV Winding

The windings are the core conductive components of the transformer, carrying the input and output of electrical energy. Kaibeite adopts the classic concentric arrangement – with the lowvoltage winding inside and the highvoltage winding outside. The LV winding is placed closer to the iron core, while the HV winding is positioned around it. This configuration optimizes insulation coordination and enhances the mechanical strength of the windings.

The HV winding features a multilayer cylindrical structure, with conductors wrapped in DMD insulating material and cooling ducts reserved between layers to ensure reliable insulation while facilitating heat dissipation.

The LV winding is wound with copper foil, which effectively reduces eddycurrent losses and improves cooling efficiency.

The insulation system of drytype transformers is typically processed by epoxy resin casting or vacuum pressure impregnation (VPI), achieving thermal classes up to Class F (155°C) or Class H (180°C). This endows the transformer with excellent overload capability and a long service life.

III. Fixing and Support System – Clamp Plates and Spacers

Core Clamp Plate

After the core laminations are stacked, they must be secured by clamp plates. The upper and lower clamp plates, together with tie rods, form an integral framework that locks the core and windings into a rigid assembly.

• The core clamp plate serves three essential functions:
• Clamping the core – preventing lamination loosening that could cause increased noise and losses;
• Providing lifting points – serving as the loadbearing points for lifting the entire coreandcoil assembly;
• Withstanding shortcircuit forces – during a system fault, enormous axial and radial electromagnetic forces are generated between windings; the strength of the clamp plates directly determines whether the transformer can withstand such impacts without displacement or damage.

Support Spacer

• Between the HV and LV windings, and between layers of coils, precise electrical clearances and physical spacing must be maintained. Support spacers, made from highstrength insulating materials (such as DMC, SMC, or epoxy resin), perform two critical tasks:
• Providing reliable electrical insulation – ensuring safe distances between high and lowvoltage sections;
• Forming cooling air ducts – allowing cooling air to flow smoothly through the windings and carry away the heat generated during operation.

IV. Electrical Connection System – Terminals, Link Rod, and Outgoing Busbar

Highvoltage Terminal & Lowvoltage Insulated Terminal

Terminals are the electrical interfaces between the transformer and the external grid. The highvoltage terminal handles the incoming connection on the HV side, while the lowvoltage insulated terminal handles the outgoing connection on the LV side, incorporating insulation structures to ensure operational safety and adequate creepage distances. The contact reliability, currentcarrying capacity, and protection class of these terminals directly affect the convenience of onsite installation and longterm operational stability.

HV Link Rod

The leads from the HV winding must be electrically connected to the bushing terminals via the HV link rod. Manufactured from highpurity oxygenfree copper, this rod features low resistance, minimal heat generation, and high mechanical strength, ensuring reliable internal connections even under longterm load fluctuations.

LV Outgoing Copper Busbar

Highcurrent output on the lowvoltage side is accomplished through the LV outgoing copper busbar. The busbar crosssection is precisely designed according to currentcarrying capacity, and its surface is tin or silverplated to reduce contact resistance, ensuring safe power transmission under highcurrent conditions.

V. Voltage Regulation System – Taps and Link Plates

HV Tap & HV Link Plate

Grid voltage is not constant. To keep the transformer output voltage within the permissible range, several taps are provided on the HV winding. By switching the link plates across these taps, the effective number of turns on the HV winding can be changed, offcircuit tap changing (or noload tap changing).

Kaibeite drytype transformers offer a standard tapping range of ±2×2.5% (five positions), sufficient to cover the vast majority of grid voltage fluctuations. Tapchanging operations are performed with the transformer deenergized, and the Operating Instructions are clearly indicated near the nameplate for convenient onsite reference by personnel.

VI. Cooling System – Radiator Fan

Drytype transformers contain no insulating oil, so cooling relies entirely on air convection. Under normal loads, natural cooling is sufficient. However, when the load increases and temperature rise becomes significant, the cooling fans are automatically activated to force cold air through the cooling ducts inside the windings, substantially boosting heat dissipation efficiency.

The fans are typically installed in groups on both sides beneath the windings, and in conjunction with a temperature control unit, they provide functions such as automatic start/stop, overtemperature alarm, and overtemperature trip. Studies indicate that forcedair cooling can improve the cooling effect by more than 50%, significantly extending insulation life and enhancing overload capacity.

VII. Lifting and Identification – Lifting Eye and Nameplate

Lifting Eye

The lifting eye is installed on top of the transformer and serves as the sole loadbearing point for lifting and handling – essential during transportation and onsite positioning. Its design and welding strength must meet the lifting requirements of the entire transformer to ensure operational safety.

Nameplate

The nameplate is the transformer's "identity card," clearly listing all key technical parameters: rated capacity, voltage class, rated current, shortcircuit impedance, connection group, insulation class, serial number, and more. The first step before installation, wiring, and commissioning is always to read the nameplate information.

VIII. Base – The Solid Foundation of the Entire Equipment

The base is the structural foundation of the transformer, supporting the full weight of the unit and transferring it to the mounting foundation. Kaibeite employs a heavyduty steel base frame with standard mounting bolt holes, ensuring the transformer is horizontally positioned and firmly secured onsite, effectively resisting vibration and shock during transportation and operation.

Conclusion

From the iron core to the windings, from clamp plates to spacers, from terminals to fans – every component may seem humble, but each performs its own essential function, and none is dispensable. Whether a drytype transformer can maintain low losses, low noise, and high reliability over a tenyear operating cycle depends entirely on whether these internal details are executed properly.

Kaibeite drytype distribution transformers, through meticulous material selection and precision manufacturing of every core component, confidently deliver stable, safe, and longlasting performance.

If you are planning projects with stringent requirements for power supply reliability and safety – such as commercial buildings, data centers, rail transit, healthcare facilities, or industrial enterprises – the Kaibeite technical team can provide tailormade drytype transformer solutions based on your actual load characteristics, installation environment, and energyefficiency needs.

Understanding the internals is the key to making an informed choice.

Keywords: drytype distribution transformer, transformer structure, Kaibeite transformer, iron core, windings, cooling fan, indoor distribution transformer