Cast Resin Dry Type Transformer – The Flame-Resistant, Silent Energy Solution!
01 General
1.1 Project Description
630 kVA dry type transformer was delivered to South Africa in 2025. The rated power of the transformer is 630 kVA with ONAN/ONAF cooling. The primary voltage is 6.6 kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 0.55 kV, they formed a vector group of Dyn11.
The cast coil transformer is a cutting-edge electrical solution designed for superior safety, efficiency, and reliability. Unlike traditional oil-filled transformers, it uses a flame-retardant epoxy resin to encapsulate the windings, eliminating the risk of oil leaks, fires, and environmental hazards.
Ideal for indoor installations, these transformers operate silently, require minimal maintenance, and are highly resistant to moisture, dust, and corrosive environments.
With excellent thermal stability and self-extinguishing properties, they ensure uninterrupted power in critical applications such as commercial buildings, hospitals, data centers, and industrial plants. Choosing a Cast Resin Dry Type Transformer means investing in a clean, eco-friendly, and long-lasting power distribution system that prioritizes safety and performance.
1.2 Technical Specification
630 kVA cast coil transformer specification and data sheet
| Delivered to | South Africa |
| Year | 2025 |
| Type | dry type transformer |
| Core material | Grain oriented silicon steel sheet |
| Standard | IEC60076 |
| Rated Power | 630kVA |
| Frequency | 50HZ |
| Vector group | Dyn11 |
| Phase | 3 |
| Cooling Type | ONAN/ONAF |
| Primary Voltage | 6.6kV |
| Secondary Voltage | 0.55kV |
| Winding Material | Aluminum |
| Impedance | 6% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5%@primary side |
| No Load Loss | 1.3KW |
| On Load Loss | 6.5KW |
1.3 Drawings
630 kVA cast coil transformer diagram drawing and size.
02 Manufacturing
2.1 Core
| The cast coil transformer constructed with high-permeability cold-rolled silicon steel laminations in a step-lap stacking configuration to reduce hysteresis and eddy current losses. The Core Type structure ensures even winding distribution and enhanced heat dissipation. With an anti-corrosive insulation coating, it delivers quiet operation, low temperature rise, and improved energy efficiency for reliable performance. |  |
2.2 Winding
 | The cast coil transformer features epoxy resin windings, ensuring superior insulation and mechanical strength. The HV/LV windings are made of aluminum conductors with interlayer insulation for enhanced dielectric strength. Bushes in the transformer are installed at winding terminals for secure electrical connections and easy maintenance. The windings are moisture-proof and dust-resistant, ideal for harsh environments. |
2.3 Final Assembly
| The cast coil transformer adopts an advanced design, featuring epoxy-resin cast windings and step-lapped cores assembled with reinforced transformer insulation brackets. The unit integrates an intelligent temperature controller and cooling fans that automatically adjust airflow based on load conditions. With fully insulated, corrosion-resistant bushings and terminals, its open-frame structure with optimized airflow channels ensures efficient heat dissipation for reliable operation under various load conditions. |  |
03 Testing
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion | |
| 1 | Measurement of winding resistance | / | Maximum resistance unbalance rate Line resistance:≤2% | HV (line) | LV (line) | Pass |
| 0.06% | 0.61% | |||||
| 2 | Measurement of voltage ratio and check of phase displacement | / | The tolerance of voltage ratio on the principal tapping: ±1/10 Connection symbol: Dyn11 | -0.02% ~ 0.16% Dyn11 | Pass | |
| 3 | Measurement of Short-circuit Impedance and Load Loss | / kW kW | t:120℃ Z%: measured value Pk: measured value Pt: measured value | 6.02% 4.55 6.28 | Pass | |
| 4 | Measurement of No-load Loss and Current at 90% and 110% of rated voltage | / kW | I0:: provide measured value P0: provide measured value | 90% Ur | 0.414 0.985 | Pass |
| 100% Ur | 0.46 1.095 | |||||
| 110% Ur | 0.506 1.204 | |||||
| 5 | Applied Voltage Test | / | HV: 20kV 60s LV: 3kV 60s | No collapse of the test voltage occurs | Pass | |
| 6 | Induced Voltage Withstand Test | / | Applied voltage (KV): 2 Ur Induced voltage (KV): 1.1 Duration(s):40 Frequency (HZ): 150 | No collapse of the test voltage occurs | Pass | |
| 7 | Partial Discharge Test | pC | The maximum level of partial discharges shall be 10 pC | ＜10 | Pass | |
04 Packing and Shipping
4.1 Packing
| The cast coil transformer is securely packed in heavy-duty plywood crates, providing robust protection during transportation and storage. Metal-reinforced edges enhance impact resistance, while custom cushioning safeguards the core and windings. External markings (center of gravity, moisture warnings, lifting points) comply with global logistics standards. |  |
4.2 Shipping
 | The transformer is shipped under CIF (Cost, Insurance & Freight) terms by sea from the Chinese main ports to Durban, South Africa. The transformer transportation includes full marine insurance covering total cargo value. Professional freight forwarding services are provided for customs clearance and inspection at the destination port. Prompt pickup upon arrival is recommended to prevent demurrage charges. |
05 Site And Summary
As a reliable solution for power systems, cast coil transformer stands out with its oil-free design, fire resistance, moisture protection, and maintenance-free operation, making it ideal for commercial buildings, industrial plants, and renewable energy applications. With precision engineering and strict quality control, every unit delivers high efficiency, safety, and durability.
By choosing us, you gain not only a superior product but also expert technical support and comprehensive after-sales service. For technical details or customized solutions, contact our engineering team today!
