10kV Epoxy Resin Cast Dry-Type Transformer

In power distribution systems, 10kV Epoxy Resin Cast Dry-Type Transformers are often the preferred choice when installation space is limited, fire safety requirements are stringent, or the use of oil-based media must be avoided. Yulan Transformer manufactures a series ranging from 30 kVA to 2500 kVA, featuring primary voltage inputs of 6 kV, 10 kV, or 35 kV and a secondary output of 0.4 kV. The windings are produced using a vacuum casting process, with insulation classes available in B, F, or H; users may opt for a protective enclosure based on site conditions.

This type of equipment is commonly found in high-rise buildings, commercial complexes, airports, rail transit stations, tunnels, chemical plants, and auxiliary systems for nuclear power stations. While the open-type structure is suitable for dedicated distribution rooms, enclosures with IP20, IP23, or higher ratings are recommended for public areas or locations requiring higher levels of protection.

Design and Manufacturing Highlights

The core is constructed from cold-rolled grain-oriented silicon steel sheets. Stacking is performed by fully automated equipment, ensuring that burr dimensions and the lamination stacking factor remain within controlled limits. Compared to manual stacking, this process reduces no-load losses by 5% to 10% and improves no-load current and noise performance.

High- and low-voltage windings are cast in epoxy resin under vacuum, forming an integral insulation layer upon curing. This structure offers high mechanical strength, enabling the transformer to withstand short-circuit electromagnetic forces. Additionally, partial discharge levels are kept below 5 pC, helping to mitigate the risk of insulation aging during long-term operation.

Insulation classes are directly linked to temperature rise: Class B corresponds to an average temperature rise of 100°C, Class F to 120°C, and Class H to 145°C. Selection should be based on a comprehensive assessment of ambient temperature, load profiles, and enclosure ventilation conditions.

Technical Specifications

Reference for Energy Efficiency and Losses

The following data applies to electrical steel strip cores and complies with the minimum energy efficiency requirements of GB 20052-2020. Load losses in the table are listed based on Class F (120°C) insulation; values for Class B and Class H differ slightly.

Note: Load losses for Class B are approximately 5% to 8% lower than the baseline, while those for Class H are approximately 6% to 9% higher. Final values are subject to the technical agreement specified at the time of order.

Production and Testing

Before leaving the factory, each unit undergoes tests including winding DC resistance, voltage ratio, insulation resistance, power-frequency withstand voltage, induced withstand voltage, no-load loss, load loss, short-circuit impedance, and partial discharge. Partial discharge testing is conducted in accordance with GB/T 7354 or IEC 60270, with measured values not exceeding 5 pC. The company holds ISO 9001:2015, ISO 14001, and ISO 45001 certifications.

Selection Guide

Q: What is the difference between open-type and enclosed (cased) dry-type transformers?

Open-type structures offer superior heat dissipation and are suitable for installation in dedicated distribution rooms where there is no risk of direct contact. Enclosed units provide a higher degree of protection but may restrict ventilation, potentially requiring capacity derating. Enclosure materials and the placement of air inlets/outlets should be determined based on the specific site environment.

Q: How do I decide between Class B and Class F insulation?

The choice depends primarily on ambient temperature and load conditions. Class B is suitable for applications with lower temperatures and stable loads. Class F is the standard choice for most indoor distribution rooms. Class H is recommended for environments with high ambient temperatures or potential short-term overloads, though this entails higher costs and larger dimensions.

Q: What is the significance of a partial discharge level below 5 pC for actual operation?

Low partial discharge indicates minimal air bubbles and impurities within the cast insulation, resulting in a dense insulation structure. During long-term operation, low partial discharge reduces insulation aging and the probability of sudden failure—a critical factor for locations requiring high power supply continuity.

Q: Can the unit be used directly in a 60 Hz system?

No; the core magnetic flux density and winding parameters must be redesigned for 60 Hz operation. 50 Hz units cannot be used directly. The frequency must be specified at the time of order, and loss and temperature rise will be verified against the specified frequency before shipment.

Q: How should the enclosure protection rating be selected?

An IP20 rating prevents the entry of foreign objects larger than 12 mm and is suitable for general indoor installations. IP23-rated units offer protection against dripping water, making them suitable for locations where exposure to water droplets is possible. Ratings of IP31 and above are intended for environments with high dust levels or stricter operational requirements. After selecting an enclosure, heat dissipation must be verified; if necessary, the unit capacity should be increased, or forced-air cooling added.

Installation and Operation Guidelines

Dry-type transformers should be installed in well-ventilated areas free from corrosive gases and conductive dust. When operating with an enclosure, air inlets and outlets must not be obstructed. Before restarting the unit after a prolonged shutdown, it is recommended to check the insulation resistance and verify that the ventilation system is functioning correctly. For installations in high-humidity or coastal regions, anti-rust treatment may be applied to the transformer core and external metal components.

Please contact the Yulan Transformer sales or technical department for dimensional drawings, foundation installation diagrams, or information regarding enclosure selection.