Cast Coil Dry Type Transformer: Built Tough for Demanding Environments.
01 General
1.1 Project Description
1500kVA cast coil dry type transformer was delivered to South Africa in 2025. The rated power of the transformer is 1500 kVA with KNAN/KNAF cooling. The primary voltage is 15 kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 0.55 kV, they formed a vector group of Dyn11.
The medium voltage dry type transformers represents the pinnacle of safety, reliability, and environmental sustainability in power distribution technology. Unlike traditional liquid-filled or ventilated dry-type transformers, its high-voltage and low-voltage windings are encapsulated with a solid epoxy resin under vacuum pressure. This advanced casting process creates a transformer that is virtually maintenance-free and impervious to harsh environments.
Our medium voltage dry type transformers is engineered for exceptional performance. It is non-flammable, emits no toxic fumes, and poses zero risk of oil leakage, making it the ideal choice for safe installation in indoor, mission-critical applications such as high-rise buildings, hospitals, data centers, industrial plants, and offshore facilities.
With superior resistance to moisture, chemicals, and contaminants, coupled with high dielectric strength and exceptional short-circuit withstand capabilities, the Cast Coil Dry Type Transformer ensures uninterrupted power supply and a long service life, providing ultimate peace of mind and lower total cost of ownership.
1.2 Technical Specification
1500 kVA medium voltage dry type transformers 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 | 1500kVA |
| Frequency | 50HZ |
| Vector group | Dyn11 |
| Phase | 3 |
| Cooling Type | ONAN/ONAF |
| Primary Voltage | 15kV |
| Secondary Voltage | 0.55kV |
| Winding Material | Aluminum |
| Impedance | 6% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5%@primary side |
| No Load Loss | 2.45KW |
| On Load Loss | 11.5KW |
| Basic impulse lighting withstand voltage primary side (BIL) | 95kV |
| Power Frequency withstand voltage-primary side | 38kV |
| Power Frequency withstand voltage-secondary side | 3kV |
| Winding temperature rise@ rated service condition | 100K |
| Insulation level | F |
1.3 Drawings
1500 kVA medium voltage dry type transformers diagram drawing and size.
02 Manufacturing
2.1 Core
The core of a medium voltage dry type transformers is typically constructed from high-grade, cold-rolled grain-oriented (CRGO) silicon steel. The laminations are precisely stacked and tightly clamped to form a robust, rigid magnetic circuit. This design minimizes core losses (hysteresis and eddy currents), ensures excellent mechanical stability to withstand short-circuit forces.
2.2 Winding
 | The winding of cast coil dry type transformer is typically made of high-conductivity copper conductors, which are precisely wound into coils and then encapsulated in epoxy resin through vacuum casting technology. This integral casting structure eliminates air gaps, providing excellent insulation performance, moisture resistance and mechanical strength, while effectively suppressing partial discharge and ensuring stable operation even in harsh environments. |
2.3 Final Assembly
| The final assembly of cast coil dry type transformer starts with placing the laminated iron core on the base frame. Then, the vacuum-cast high-voltage and low-voltage windings are hoisted and concentrically mounted on the core columns, with insulation spacers installed to maintain precise gaps. Next, lead wires are connected to terminal blocks, cooling fans (if equipped) and temperature monitoring devices are mounted, followed by fitting the protective enclosure. Final electrical tests ensure assembly compliance. |  |
03 Testing
Tests for medium voltage dry type transformers, such as the 1500kVA-15/0.55kV model, adhere to IEC 60076 series standards (1, 3, 11) and include key routine items: winding resistance measurement (verifying unbalance ≤2%), voltage ratio/phase displacement check (Dyn11, deviation ±1/10), short-circuit impedance/load loss and no-load loss/current tests, dielectric tests (38kV applied voltage for 60s, 1.1kV induced voltage at 150Hz for 40s), and partial discharge test (max ≤10pC), all confirming qualified electrical and insulation performance.
| 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 |
| 0.17% | 0.32% | |||||
| 2 | Measurement of voltage ratio and check of phase displacement | / | The tolerance of voltage ratio on the principal tapping: ±1/10 Connection symbol: Dyn11 | 0.03% ~ 0.19% Dyn11 | Pass | |
| 3 | Measurement of Short-circuit Impedance and Load Loss | / kW kW | t:120℃ Z%: measured value Pk: measured value Pt: measured value | 6.01% 8.437 10.437 | 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 | 0.27 2.331 | Pass |
| 100% Ur | 0.30 2.59 | |||||
| 110% Ur | 0.33 2.849 | |||||
| 5 | Applied Voltage Test | / | HV: 38kV 60s LV: 5kV 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 dry type transformer is packed in a strong wooden case. Inside, it is wrapped with shock-absorbing foam to avoid collision damage, firmly fixed with metal fasteners to prevent shifting, and the outer case is printed with clear shipping marks, product model and weight for easy handling. |  |
4.2 Shipping
 | Under CIF terms, the medium voltage dry type transformers (in sturdy wooden cases) is shipped to Durban. The seller organizes ocean transportation, pays freight, and buys insurance against loss/damage during transit. Delivery is completed when the goods are on the carrying vessel, and the cargo will be delivered to Durban port as scheduled. |
05 Site And Summary
With its robust cast resin encapsulation, reliable dry-type design, and consistent performance, our cast coil dry type transformer stands as a trustworthy power solution for diverse industrial, commercial, and infrastructure needs. Engineered for safety, low maintenance, and adaptability to varying operating conditions, it delivers steady power support to keep your operations running smoothly. Whether you’re seeking durability, efficiency, or compliance with strict standards, we’re ready to assist-let this transformer elevate your power system reliability.
