Three-Dimensional Wound Core Cast Resin Dry-Type Transformer

Description

Overview

The three-dimensional wound core resin-insulated dry-type transformer is a perfect combination of the three-dimensional wound core and the resin-insulated dry-type transformer.

This product not only inherits the advantages of the three-dimensional wound core, such as energy saving, material saving, low no-load loss, low no-load current and low noise, but also features excellent electrical performance, low partial discharge, high lightning impulse resistance, strong short-circuit withstand capability and high mechanical strength from the resin-insulated dry-type transformer.

It is a dual energy-saving product for both manufacturing and operation, and its application and promotion are in line with China’s national energy conservation and emission reduction policies.

The production of this product utilizes 21 patented technologies developed by our company. We have also developed a full set of specialized production equipment to support its manufacturing.

This product is suitable for environments with high fire protection requirements, including high-rise buildings, airports, railway stations, ports, subways, hospitals, power plants, metallurgical industries, shopping malls, densely populated residential areas, petrochemical plants, nuclear power stations and nuclear submarines.

As a new high-tech transformer product, the three-dimensional wound core resin-insulated dry-type transformer provides an advanced solution featuring energy efficiency, environmental friendliness, excellent weather resistance and superior electrical performance.

Product structure

• The three-dimensional triangular structure realizes a more optimized arrangement of the iron core. Three identical single-frame cores are assembled into a three-dimensional equilateral triangle, ensuring fully symmetrical and equal-length magnetic paths for the three-phase iron core, balancing three-phase power supply, significantly reducing magnetic resistance, and drastically cutting excitation current and no-load loss.
• The iron core curing adopts the proprietary curing process exclusive to three-dimensional triangular wound cores, delivering excellent curing effect. This process guarantees no deformation of the iron core during assembly, transportation and operation, further reducing no-load loss and noise of the iron core.

Key Advantages of This Structure

1. Significant Energy Saving

The three-dimensional triangular wound core is seamless, eliminating high-energy-consumption zones. It fully leverages the high magnetic permeability of premium iron core materials, minimizing the loss caused by air gaps at joints.

2. Compact Miniaturized Design

With a high space utilization rate, the triangular structure of the transformer results in a smaller volume than conventional transformers, featuring a compact structure, attractive appearance and minimal floor space.

3. Ultra-low Noise

The three-dimensional triangular wound core is wound sequentially with trapezoidal silicon steel strips, ensuring tight lamination between strips. The magnetic permeability direction of the silicon steel strip is fully aligned with the magnetic path direction of the iron core, resulting in minimal vibration during operation. This structure effectively eliminates the noise generated by discontinuous magnetic paths in laminated cores, reducing noise to the lowest possible level.

Winding

The coil consists of a high-voltage coil and a low-voltage coil. The low-voltage coil adopts a foil or cylindrical structure, with its end insulation sealed by resin mixture. The high-voltage coil adopts a sectional cylindrical structure, and the entire coil conductor is encapsulated by a solid epoxy resin insulation layer.
According to the capacity of the transformer, axial heat dissipation ducts for bidirectional heat dissipation are arranged inside the coil.
Interlayer insulation is made of high-grade DMD prepreg and formed by hot curing. After winding processing, the product is cured in an oven to form a winding with excellent short-circuit withstand capability. Meanwhile, for transformers with a capacity of 315kVA and above, foil windings are adopted for the low-voltage side.

The low-voltage foil winding offers the following advantages:
• No helix angle at both ends of the coil, greatly reducing unbalanced ampere-turns and significantly enhancing short-circuit withstand capability.
• Winding turns are arranged along the width, allowing more flexible and applicable heat dissipation ducts and excellent heat dissipation performance.
• High inter-turn capacitance and low potential gradient, resulting in strong impulse voltage withstand capability.
The high-voltage coil adopts a sectional cylindrical structure, and the entire conductor is encapsulated by a solid epoxy resin insulation layer. High-grade insulating materials for epoxy resin and curing agent are supplied by HUNTSMAN Advanced Materials. The coil conductor and resin insulation layer form an integral rigid body with excellent mechanical strength and strong short-circuit withstand capability, as well as high dielectric strength of epoxy resin.
In addition, since the entire coil conductor is encapsulated by solid epoxy resin, moisture intrusion is effectively prevented, and the conductor is fully protected from corrosion by various harmful gases and corrosive chemicals, providing excellent moisture-proof and anti-fouling performance.

Electromagnetic Wire

Our company adopts the N758 paper-covered wire developed in cooperation with DuPont. The insulation thickness of the N758 electromagnetic wire is merely 0.16mm, while it boasts a high minimum breakdown voltage.

On the premise of meeting the electrical performance requirements of transformers, this wire can reduce the volume of transformer coils and cut down the consumption of raw materials, thus saving the usage of wire materials and silicon steel sheets. For transformers with the same capacity, adopting N758 paper-covered wire can save 0.4% of electromagnetic wire and 1% of silicon steel sheets.

Thanks to the relatively thin insulation layer of N758 paper-covered wire, the coils using this wire contribute to a smaller transformer size, as well as lower consumption of electromagnetic wire and silicon steel sheets. Therefore, N758 paper-covered wire has a more competitive price than the double glass fiber covered wire (SBEB) used in traditional epoxy resin transformers, which further enhances the economic efficiency of the transformer.

Vacuum Pressure Casting

High-voltage Casting Structure with Thin Insulation

The high-voltage winding adopts a thin-insulation casting structure, which is cast with epoxy resin mixed filler under a vacuum state of 3-5MPa. During the entire casting process, the temperature and vacuum degree of each technological procedure are strictly controlled, including baking, preheating, casting, vacuum maintenance, pressure relief, gelation, curing and demolding, so as to eliminate defects such as bubbles and cracks in the winding after casting.

The poured resin mixture can fully penetrate into all gaps of the coil, avoiding the existence of voids and effectively suppressing the occurrence of partial discharge. The partial discharge level is no more than 10pC.

Technical Parameters

1) SCB Series Epoxy Resin Casting Class F Dry-Type Transformer

Overload capacity (transformer in forcing in forced-air cooling situation satisfies)