Reliable and efficient dry type VPI transformer for industrial power distribution
01 General
1.1 Project Description
The project adopts a 315kVA VPI dry type transformer, built with an open winding, non–cast resin design and manufactured in accordance with IEC 60076. It is configured for 11kV on the primary side and 0.55kV on the secondary, with a Dyn11 vector group, which fits naturally into South Africa’s medium- to low-voltage distribution practice. In many industrial and commercial networks across the country, 11kV is the most commonly used distribution voltage, and this configuration reflects that reality rather than an abstract specification. Designed impedance of 4%, balancing short-circuit current limitation and voltage regulation.
South Africa’s industrial landscape spans energy-intensive sectors such as mining, manufacturing, processing plants and large infrastructure facilities, where power supply is expected to be stable and continuous. At the same time, much of the country experiences high ambient temperatures, strong solar radiation and long operating hours, especially in inland industrial regions. These conditions add thermal stress to electrical equipment. To respond to this environment, the dry transformer is designed with H-class insulation, a 100K temperature rise limit and an AN/AF cooling system, providing the thermal endurance, insulation reliability and operating stability needed for sustained operation under the elevated ambient temperatures typical of South Africa.
1.2 Technical Specification
315 kVA dry type vpi transformer specification and data sheet
| Delivered to | South Africa |
| Year | 2025 |
| Type | Open winding type, not epoxy resin cast type |
| Standard | IEC60076 |
| Rated Power | 315KVA |
| Frequency | 50HZ |
| Phase | three |
| Cooling Type | AN/AF |
| Primary Voltage | 11 kV |
| Secondary Voltage | 0.55 kV |
| Vector Group | Dyn11 |
| Winding Material | Aluminum |
| Impedance | 4% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5%@primary side |
| No Load Loss | 1.1 kW |
| On Load Loss | 4.1 kW |
| Winding temperature rise @ rated service condition | 100 K |
| Insulation level | H |
| Accessories | 110V power supply voltage fans |
1.3 Drawings
315 kVA dry type vpi transformer drawing
02 Manufacturing
2.1 Cooling System
An AN/AF cooling method is applied, allowing the transformer to operate under natural air cooling during normal load conditions and switch to forced air cooling when required. The cooling system features: temperature-controlled cooling fans, a 110V fan power supply, and enhanced heat dissipation during high ambient temperature or short-term overload conditions. |  |
2.2 Core
 | The dry type VPI transformer uses a high-quality laminated silicon steel core, which is key for reliable operation. The core is carefully stacked and clamped to keep magnetic alignment precise, vibration low, and flux paths optimized. Thanks to this, the transformer has a no-load loss of just 1.1 kW and a load loss of 4.1 kW, keeping noise and heating down. These design details help maintain stable magnetic performance, good efficiency, and long-term reliability, making it ideal for continuous operation in South Africa’s industrial power networks. |
2.3 Winding
High-quality aluminum conductors form the transformer windings; carefully vacuum-pressure impregnated, they gain mechanical strength and reliable insulation. Between the phase windings, phase separation boards add extra physical insulation, improving dielectric performance. Stable operation, reduced inter-phase stress, long-term reliability – all achieved even in demanding industrial environments. |  |
2.4 H-Class Insulation
An H-class insulation system, rated for a thermal class of 180°C, is combined with a 100K temperature rise design to provide a strong thermal safety margin. This approach offers several practical advantages: lower actual operating temperatures under rated load, reduced insulation aging rate, and improved long-term reliability for continuous-duty applications.
03 Application and Installation
This 315kVA 11kV VPI dry type transformer fits a wide range of industrial uses, manufacturing plants, water and wastewater pump stations, commercial facilities, indoor substations; reliable operation, good thermal performance, easy integration into existing systems – all make it a solid choice for industrial power distribution across South Africa.
04 Packing and Shipping
05 Site and Summary
Designed for South Africa’s operating conditions and typical distribution practices; combines dependable electrical performance, efficient cooling, and robust insulation. With H-class insulation, a 100K temperature rise, and proven VPI technology; handles the heat, the load, long operating hours – delivers a reliable, cost-effective solution for medium-voltage industrial distribution.
