3 Phase Step Up Transformer 400V to 35kV (1–20 MVA Power Transformer)
The three-phase step-up transformer (400V to 35kV) is engineered to efficiently raise low-voltage power (400V) to medium voltage (35kV). This voltage transformation reduces current, minimizes transmission losses, and enables smooth grid integration for solar plants, industrial power systems, rural distribution networks, and commercial microgrids.
Technical Overview of the 3 MVA 400V to 35kV Transformer
A 3 MVA step-up transformer handles 3 million volt-amperes of apparent power. It uses a 400V LV input and delivers a 35kV HV output. The transformer’s core function is to increase voltage while reducing current, significantly improving long-distance transmission efficiency based on the formula Ploss = I²R.
Most 3 MVA transformers adopt an oil-immersed, air-cooled ONAN/ONAF design. Insulating oil provides superior thermal management, while natural or forced air cooling ensures stable operation in hot or remote environments. These transformers typically achieve over 98.5% efficiency and comply with IEC 60076 and ANSI C57.12.00 standards.
20 MVA Step Up Transformer 400V to 35kV – Application Fields
The combination of a universal 400V input and 35kV medium-voltage output makes this transformer suitable for solar PV stations, industrial power systems, rural transmission, and data centers.
Solar Power Plants (10–20 MW)
Solar inverters output 400V, requiring voltage boosting to connect to 35kV distribution grids. The 3 MVA transformer is the ideal match for 3 MW inverter blocks.
Case Study: 15 MW Solar Farm (Australia)
A Queensland project used five 3 MVA 400V-to-35kV transformers to connect 15 MW of solar generation to the 35kV grid. ONAF cooling ensured stable performance during 40°C summers, achieving 98.7% efficiency and zero downtime in 18 months.
Industrial Captive Power Plants
Factories with diesel or gas generators producing 400V can feed power into 35kV grids or operate heavy machinery via higher voltage distribution.
Example: Textile Mill (India)
A Gujarat mill equipped with a 3 MW diesel generator used a 3 MVA step-up transformer to export surplus energy to the 35kV state grid, reducing electricity costs by 20%.
Rural & Remote Power Transmission
Rural generators (hydro, wind, diesel) often output 400V, which must be boosted to 35kV for efficient long-distance transmission. This reduces line losses from 15% to 2–3%.
Use Case: Village Electrification (Kenya)
A 5 MW hydro plant used two 3 MVA 400V-to-35kV transformers to deliver power across 35 km to 12 villages, supplying electricity to 5,000 homes.
Data Centers & Microgrids
Large data centers using 400V backup generators rely on 3 MVA step-up transformers to connect to 35kV grids, ensuring uninterrupted supply and system redundancy.
Example: Data Center (Germany)
A 50,000 sq. ft. facility used a 3 MVA transformer for seamless switching between generator backup and the 35kV utility grid, achieving 99.99% power uptime.
Advantages of the 3 MVA 400V to 35kV Step Up Transformer
Ideal Capacity for Medium-Scale Projects
The 3 MVA rating matches common 3 MW inverters and generators, preventing efficiency losses caused by oversizing or undersizing transformer capacity.
Low Transmission Losses
Stepping up from 400V to 35kV reduces current by approximately 82 times, lowering energy losses from 10–15% to around 2–3%.
Cost-Effective Operation & Long Service Life
Oil-immersed insulation protects windings from dust and moisture, minimizing maintenance. The typical lifespan of 25–30 years reduces long-term replacement costs.
Compact and Space-Saving
3 MVA units provide a smaller footprint compared with larger transformers, making them suitable for industrial plants and land-restricted solar facilities.
Global Grid Compatibility
The 35kV output supports medium-voltage distribution systems globally, including Europe, Asia, Africa, and Australia. This ensures easy grid connection without additional voltage conversion equipment.
Technical Specifications of Three Phase Step up Transformer 400V to 35kV 20 MVA
Below is a standard technical table (values may vary by manufacturer; customizations are available for specific projects):
| Parameter | Specification |
|---|---|
| Apparent Power (Rating) | 1/5/10/20 MVA |
| Phase Configuration | Three-Phase, 50 Hz / 60 Hz (customizable) |
| Voltage Ratio | Primary (LV): 35/33/22/24/20kV; Secondary (HV): 400v/800v/11kv/22kv |
| Cooling Method | ONAN (Oil Natural Air Natural) / ONAF (Oil Natural Air Forced) |
| Insulation Class | Class B (130°C) – suitable for high-temperature environments |
| Temperature Rise Limit | Oil: ≤ 60°C (above ambient); Winding: ≤ 70°C (above ambient) |
| Connection Group | Dyn11 (standard for step-up transformers; ensures phase alignment) |
| Impedance Voltage | 6.5% – 8% (at rated current, 75°C; minimizes voltage fluctuations) |
| No-Load Loss | ≤ 6.5 kW (low energy waste when idle) |
| Load Loss (at Rated Current) | ≤ 28 kW (minimizes energy loss during full-load operation) |
| Insulation Resistance | ≥ 1000 MΩ (at 25°C, HV-LV, HV-Earth, LV-Earth) |
| Winding Material | Copper (high conductivity; optional aluminum for cost savings) |
| Tank Material | Carbon Steel (anti-corrosion painted for outdoor use) |
| Protection Features | Buchholz relay (internal fault detection), pressure relief valve, oil level gauge, temperature sensor |
| Weight (Approx.) | 4,500 – 6,000 kg (core, windings, oil, and tank) |
| Standards Compliance | IEC 60076 (International), ANSI C57.12.00 (USA), AS/NZS 60076 (Australia), IS 2026 (India) |
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