High-Performance Traction Transformers – Engineered for Speed & Safety!
01 General
1.1 Project Description
5 MVA railway transformer was delivered to Canada in 2025. The rated power of the railway transformer is 5000 kVA with ONAN cooling. The primary voltage is 44 kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 6.6 kV, they formed a vector group of Dyn11.
This traction transformer is designed to meet the power supply demands of traction substations, providing electricity for 11 kV and 6.6 kV transmission line systems. It features a well – structured design with specific accessory requirements, including a no – load tap – changing switch, detachable hot – dip galvanized radiators, and various valves and monitoring devices. The transformer tank is constructed with steel plates (≥6mm for the tank, 16mm for the bottom plate) and has a rational layout of (bushings), rods, and terminals (with specified diameters for different connections). Special considerations are given to harmonic tolerance, mechanical strength of windings, and anti – pollution design (with defined color schemes and pollution – resistant thickness). It is engineered to ensure reliable operation, efficient heat dissipation, and convenient maintenance, playing a crucial role in the traction power supply system.
1.2 Technical Specification
75 kVA railway transformer specifications type and data sheet
| Delivered to | South Africa |
| Year | 2025 |
| Type | Pole mounted transformer |
| Standard | IEC60076 |
| Rated Power | 5000 kVA |
| Frequency | 50HZ |
| Phase | 3 |
| Cooling Type | ONAN |
| Primary Voltage | 44 kV |
| Secondary Voltage | 6.6 kV |
| Winding Material | Copper |
| Angular displacement | Dyn11 |
| Impedance | 7% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 4.54 kW |
| On Load Loss | 35 kW |
1.3 Drawings
5000 kVA traction transformer diagram drawing and size.
02 Manufacturing
2.1 Core
| The railway transformer employs a three-phase three-limb stacked laminated core, constructed from thin silicon steel laminations (0.23–0.35mm) with insulated coatings to minimize eddy current losses. Precision-stacked with step-lap joints, the design ensures low no-load loss, balanced flux distribution, and high mechanical strength to withstand railway vibrations. Its compact three-limb structure optimizes magnetic efficiency while reducing weight, making it ideal for high-performance traction power systems. |  |
2.2 Winding
 | The railway transformer utilizes continuous winding for optimal performance in demanding railway applications. This robust design features interlocked disc coils that provide exceptional mechanical strength to withstand vibration and short-circuit forces, while maintaining precise electrical characteristics. The winding’s vertical oil ducts ensure efficient cooling, and its transposed conductor construction minimizes eddy current losses. The continuous disc configuration offers superior surge voltage withstand capability and uniform temperature distribution, making it ideal for handling the frequent load variations inherent in traction power systems. This compact yet durable winding solution combines reliability with high electrical and thermal performance. |
2.3 Tank
| The traction transformer features a gray-painted tank with a white-colored conservator (oil tank), ensuring clear visual identification. The tank is constructed with hot dip galvanized removable radiators for enhanced corrosion resistance and efficient heat dissipation. For maintenance access, inspection covers or manholes are securely fastened with bolts and gasket seals to prevent oil leakage. Each cover is equipped with sturdy lifting handles for safe and convenient removal during servicing. This robust design ensures durability, weather resistance, and easy maintenance in demanding railway environments. |  |
2.4 Final Assembly
 | 1. Winding Assembly: Slide pre-fabricated LV (low-voltage) and HV (high-voltage) windings onto the core, ensuring proper alignment of insulation components (spacers, blocks) and tightening the windings. 2. Electrical Connections: Perform welding or bolted connections for winding leads, install tap changers, insulate joints, and secure all connections. 3. Core-Coil Drying: Place the assembled active part into a drying oven for vacuum hot-air drying to remove moisture, then verify insulation resistance meets standards. 4. Tank Assembly: Lift the dried active part into the tank, align and secure it, then bolt and seal the lower tank section. 5. Accessory Installation: Mount bushings, conservator, pressure relief valve, temperature gauges, Buchholz relay, and other accessories, connecting pipelines and monitoring circuits. 6. Oil Filling & Sealing: Perform vacuum oil filling to the specified level, conduct leak tests |
03 Testing
1. Measurement of dissolved gasses in dielectric liquid from each separate oil compartment except diverter switch compartment
2. Measurement of voltage ratio and check of phase displacement
3. Measurement of winding resistance
4. Measurement Of D.C Insulation Resistance Between Each Winding To Earth And Between Windings
5. Determination of capacitances windings to earth and between windings
6. Applied Voltage Test (AV)
7. Measurement of No-load Loss and Current
8. Induced Voltage Withstand Test
9. Measurement of Short-circuit Impedance and Load Loss
10. Measurement of dissolved gasses in dielectric liquid from each separate oil compartment except diverter switch compartment
11. Leak Testing With Pressure For Liquid-Immersed Transformers (Tightness Test)
04 Packing and Shipping
4.1 Packing
| The railway transformer is securely mounted inside a reinforced wooden crate using bolts or steel straps, with vulnerable parts like bushings wrapped in shock-absorbing material. The tank is either oil-filled or filled with dry air/nitrogen, and the crate is lined with moisture-proof film and sealed with waterproof tape. The sturdy wooden structure features forklift slots/lifting lugs, steel band reinforcement, and a sloped rain cover. External markings include weight, dimensions, handling symbols, and hazard labels, while internal documents (packing list, manuals, test reports) are stored in a waterproof pouch. |  |
4.2 Shipping
 | The railway transformer is securely loaded onto a flatbed truck and transported to the port of shipment. For CIF terms, the supplier handles sea freight, including booking a suitable vessel with proper stabilization (e.g., twist locks for containers or lashing for breakbulk). The wooden crate is stowed to avoid moisture exposure, with shock/vibration indicators attached. Insurance covers marine risks (All Risks per ICC Clause A). Upon arrival at Durban port, the cargo is offloaded using port cranes, cleared through customs (supplier arranges export docs; buyer handles import clearance), and delivered to the consignee’s specified location. Specialized trailers may be needed for oversized units. |
05 Site And Summary
As a cornerstone of rail traction and power systems, our traction transformers deliver unmatched reliability, efficiency, and compactness for global railways, metros, and hybrid locomotives. Featuring modular design, premium insulation, and smart monitoring, they excel in harsh environments with minimal loss, noise, and extended lifespan. Backed by customized solutions and lifecycle management, we ensure seamless support from design to global delivery. Contact us for technical specs or case studies – powering your mobility future with confidence.
