Green innovation, energy-saving pioneer—Three-phase pad-mounted transformers, leading the era of sustainable power!
01 General
1.1 Project Description
300 kVA pad mount transformer was delivered to America in 2024. The rated power of the transformer is 300 kVA with ONAN cooling. The primary voltage is 12.47GrdY/7.2 kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 0.48/0.277 kV, they formed a vector group of YNyn0, The advantages are high voltage quality, neutral point does not drift, box does not heat, low noise, good lightning protection. It is a loop feed and dead front transformer. pad mounted transformer can be used indoors or outdoors, widely used in industrial parks, residential areas, commercial centers and high-rise buildings and other places.
It is worth mentioning that the dielectric coolant in the transformer use highly refined Type II inhibited new mineral oil. Bayonet with current limiting fuses. The high-voltage overcurrent protection scheme provided with the transformer is an externally removable loadbreak expulsion Bay-O-Net fuse assembly with a flapper valve to minimize oil spillage. The bayonet fuses are in series with ELSP under-oil partial-range current limiting back-up fuses with an interrupting rating of 50,000 RMS symmetrical amperes interrupting with minimum melting current approximately 200% of transformer nameplate rating.
1.2 Technical Specification
300 kVA pad mount transformer specifications type and data sheet
| Delivered to | America |
| Year | 2024 |
| Type | Pad mounted transformer |
| Standard | IEEE Std C57.12.34-2022 |
| Rated Power | 300KVA |
| Frequency | 60HZ |
| Phase | 3 |
| Feed | Loop |
| Front | Dead |
| Cooling Type | ONAN |
| Primary Voltage | 12.47GRDY/7.2 KV |
| Secondary Voltage | 0.48/0.277 KV |
| Winding Material | Aluminum |
| Angular displacement | YNyn0 |
| Impedance | 4% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 0.45KW |
| On Load Loss | 2.925KW |
| Accessories | Standard Configuration |
1.3 Drawings
300 kVA pad mount transformer diagram drawing and size.
02 Manufacturing
2.1 Core
Advantages of the Three-Phase Five-Limb Core
Clamping Devices Function: Secure the core and prevent the silicon steel sheets from loosening; support the weight of the core and windings. Tie Plates Function: Fasten the upper and lower clamping devices using bolts, provide lateral pressure, and prevent the core from loosening. |  |
2.2 Winding
 | The coil is insulated with B-stage, epoxy coated, diamond pattern, insulating paper, which is thermally cured under pressure to ensure proper bonding of conductor and paper. The coil has been vacuum processed to ensure maximum penetration of insulating fluid into the coil insulation system. The combination of low-voltage foil winding and high-voltage wire winding achieves low load loss and short-circuit impedance, meeting diverse load requirements. Ensures electrical isolation between high-voltage and low-voltage windings, enhancing safety. The mechanical stability of the foil winding and the insulation reliability of the wire winding improve the transformer’s operational life. Strong resistance to short circuits and vibrations makes it suitable for harsh operating environments. |
2.3 Tank
| The transformer tank is made of 304 stainless steel, The tank base is designed to allow skidding or rolling in any direction. Lifting provisions consist of four lifting lugs welded to the tank. The transformer adopts sealed tank construction of sufficient strength to withstand a pressure of 7 psig without permanent distortion, and 15 psig without rupturing or affecting cabinet security. The tank include a pressure relief device as a means to relieve pressure in excess of pressure resulting from normal operation. The venting and sealing characteristics shall be as follows:
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2.4 Final Assembly
 | Core Component Installation: Fix the core and windings into the oil tank, connect high- and low-voltage leads, and install insulation and shielding components to ensure reliable electrical connections. Accessory Installation: Install accessories such as the oil level gauge, temperature gauge, and cooling fins. Connect the terminal box and control units, completing the installation of protective devices. Enclosure and Sealing: Mount the metal enclosure to seal the oil tank, check and seal joints to ensure moisture and leak resistance. Testing and Oil Filling: Perform electrical and mechanical performance tests, fill the oil tank with insulating oil, remove bubbles, and conduct a gas-tightness test. |
03 Testing
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | % | Maximum resistance unbalance rate | 0.37 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤0.5% | -0.05 | Pass |
| 3 | Phase-relation tests | / | YNyn0 | YNyn0 | Pass |
| 4 | No-load losses and excitation current | % | I0 :: provide measured value | 0.28 | Pass |
| kW | P0: provide measured value(at 20 ℃) | 0.412 | |||
| / | the tolerance for no load loss is ±10% | / | |||
| 5 | Load losses , impedance voltage, total losses and efficiency | / | t:85℃ the tolerance for impedance is ±7.5% the tolerance for total load loss is ±6% | / | Pass |
| % | Z%: measured value | 3.86 | |||
| kW | Pk: measured value | 2.822 | |||
| kW | Pt: measured value | 3.234 | |||
| % | Efficiency not less than 99.27% | 99.30 | |||
| 6 | Applied Voltage Test | / | HV: 34kV 60s LV: 10kV 60s | No collapse of the test voltage occurs | Pass |
| 7 | Induced Voltage Withstand Test | / | Applied voltage (KV):0.96 | No collapse of the test voltage occurs | Pass |
| Duration(s):48 | |||||
| Frequency (HZ): 150 | |||||
| 8 | Insulation Resistance Measurement | GΩ | HV-LV to Ground: | 85.3 | / |
| LV-HV to Ground: | 95.2 | ||||
| HV&LV to Ground: | 90.1 | ||||
| 9 | Leakage Test | / | Applied pressure：20kPA | No leakage and no Damage | Pass |
| Duration：12h | |||||
| 10 | Oil Test | kV | Dielectric Strength | 56.9 | Pass |
| mg/kg | Moisture Content | 9.9 | |||
| % | Dissipation Factor | 0.0274 | |||
| mg/kg | Furan Analysis | / | |||
| / | Gas Chromatography Analysis | / |
04 Packing and Shipping
05 Site And Summary
In today’s rapidly evolving power industry, the 300 kVA pad mount transformer has become an indispensable component of power distribution systems due to its outstanding performance and reliability. Whether in residential, commercial, or industrial applications, its compact design, ease of maintenance, and excellent environmental resilience make it capable of meeting various complex power demands. Choosing our three phase pad mounted transformer is not only a choice for an efficient power solution but also a commitment to safety and sustainability. We are dedicated to providing our customers with exceptional products and services, helping you achieve maximum benefits in modern power systems.
