01 General
1.1 Project Description
This project supports an indoor medium-voltage distribution system at an industrial facility in South Africa. The utility supply comes in at 6.6 kV and is stepped down to 0.55 kV to feed production lines and a variety of auxiliary loads across the plant.
The 1500 kVA cast resin transformer is installed indoors. Space is limited, but the operating conditions are anything but mild. Ambient temperatures can get high, and the load profile is constantly changing. Continuous operation is expected-day in, day out-with very little tolerance for unexpected downtime. These factors influenced many of the design decisions right from the start.
1.2 Customer Requirements
From the customer’s side, the expectations were clear. They needed a large-capacity dry type transformer suitable for indoor installation-one that avoids the fire and environmental concerns commonly associated with oil-filled equipment.
Thermal performance was another key point. The 1500 kVA cast resin transformer had to remain stable under variable loading, including peak demand periods, without relying on constant manual intervention. Automatic cooling control was therefore essential, not as an extra feature, but as a practical requirement for reliable daily operation.
1.3 Technical Specification
1500kVA cast coil dry type transformer specification and data sheet
| Delivered to | South Africa |
| Year | 2025 |
| Type | cast coil dry type transformer |
| Standard | IEC60076 |
| Rated Power | 1500KVA |
| Frequency | 50HZ |
| Phase | three |
| Number of windings | 2 |
| Cooling Type | AN/AF |
| Primary Voltage | 6.6 kV |
| Secondary Voltage | 0.55 kV |
| Vector Group | Dyn11 |
| Winding Material | Aluminum |
| Core material | Grain oriented silicon steel sheet |
| Insulation level | F |
| Impedance | 6% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 2.45 kW |
| On Load Loss | 11.73 kW |
| Accessories | With Temperature Controller & Cooling Fans |
1.4 Drawings
1500kVA cast coil dry type transformer drawing
02 Design Features
2.1 Core–Winding Design
  | At the core of the project is a 1500 kVA, three-phase cast coil dry type transformer designed for 50 Hz operation. The primary voltage is rated at 6.6 kV, with a 0.55 kV secondary, configured in a Dyn11 vector group-well suited for industrial low-voltage distribution systems. System coordination was addressed through a 6% impedance level, while an off-circuit tap changer (NLTC) with a ±2 × 2.5% tapping range allows voltage adjustment during installation or grid condition changes. For the magnetic circuit, grain-oriented silicon steel is used to keep no-load losses under control. Aluminum windings were selected for the high-current industrial application, balancing electrical performance, thermal behavior, and overall system economics. Nothing exotic-just proven design choices applied where they make sense. |
2.2 Insulation System
The insulation system is rated Class F, providing sufficient thermal margin for continuous operation under demanding conditions. All windings are fully encapsulated in cast resin, which adds mechanical strength and helps maintain insulation stability over time.
Because this is a dry type design, there is no insulating oil at all. No leakage risk. No fire spread concerns linked to liquid insulation. That makes the transformer particularly suitable for enclosed indoor electrical rooms, where safety, compliance, and ease of operation all matter.
2.3 Loss Performance and Energy Efficiency
| Loss performance was addressed early in the design phase. The transformer achieves a no-load loss of 2.45 kW and an on-load loss of 11.73 kW, based on optimized magnetic flux levels and conductor design. Over the long term, this translates into predictable efficiency and reduced operating losses-important for equipment that runs continuously and forms a permanent part of the facility’s power infrastructure. It’s not about chasing numbers on paper, but about steady, reliable performance over years of service. |  |
03 Cooling System And Thermal Management
3.1 Forced Air Cooling Fans
Six cooling fans are installed to provide forced air cooling for the transformer. Each fan operates at 1400 r/min with a rated power of 45 W and is supplied by AC 220 V. The fans deliver an airflow of approximately 770 m³/h per unit while maintaining low operating noise of ≤52 dB, ensuring stable heat dissipation, quiet operation, and reliable performance during long-term continuous service.
3.2 Temperature Controller
Safe operation of dry-type transformers depends on accurate winding temperature control. This temperature controller uses embedded platinum resistance sensors and microprocessor-based technology to monitor winding temperature with high accuracy and 0.1 °C resolution. Automatically controls cooling fans, with over-temperature alarm and trip outputs for protection. Powered by AC 220 V, suitable for both 50/60 Hz systems; designed to deliver stable and reliable thermal protection during continuous transformer operation.
04 Packing and transportation
05 Site and Summary
This cast resin dry-type transformer has been successfully deployed in an industrial facility in South Africa, providing reliable, safe, and energy-efficient power distribution. Its custom design ensures stable operation under continuous and variable loads, making it an ideal solution for industrial medium-voltage distribution networks where uptime, safety, and efficiency are critical.
