3750kVA Three Phase Pad Mounted Transformer
NPC ELECTRIC's 3750kVA Three Phase Pad Mounted Transformer is a heavy-duty, oil-immersed compartmental-type distribution transformer engineered for high-capacity underground power distribution in large-scale utility and industrial settings. This high-power pad-mounted transformer reduces energy consumption, lowers total ownership costs through superior efficiency and longevity (30+ years), and supports demanding loads with features like vacuum fault interrupters and harmonic mitigation, ideal for reliable, secure power in expansive commercial-industrial networks.
- Primary Voltage Ratings 34.5-19.92/13.8-7.957/13.2-7.62/12.47-7.2 or others
- Secondary Voltage Ratings 208GrdY/120;416GrdY/240 or Customized
- H.V. Tap Range ± 2×2.5% HV taps or others
- Type Loop Feed or Radial Feed
- BIL 30/95kV
- Standards IEEE, ANSI, NEMA, ASTM
- Application Renewable energy farms (solar/wind step-up), large-scale EV charging
- Power Rating 3750kVA
- Certificate UL
- Cooling Method ONAN, ONAN/ONAF, KNAN, KNAN/KNAF
- Oil Mineral Oil or FR3
- Opeartion Step Down & Step Up
Technical Specifications
Customization Optional
Packing and Shipping
Manufacturer Test
Routine Testing
Application
Technical Specifications
3750kVA Three Phase Pad Mounted Transformer
Technical Specifications
Accessories
| Rated Power | 3750kVA |
| Rating Primary Voltage | 4.16-34.5kV or customized |
| Secondary Voltage | 480GrdY/277 208GrdY/120 400GrdY/230 Customized（208Y/120 V to 4,160 V） |
| Frequency | 50/60Hz |
| Vector Group | Dyn1/Yyn0/Dyn11/Dyn5 |
| Winding Material | Aluminum/Copper |
| Efficiency | As IEEE,Doe 2016,CAS Std or Customized |
| Impedance Voltage | Nominal 3.5% or Customized 1.1-5.75% |
| Altitude | ≤1,000m or Customized |
| Color | ANSI 70 Light gray/Munsell 7GY3.29/1.5 or customized etc |
| Tank material | Mild Steel, 304 Stainless Steel |
| Insulating Oil Weight | 3500 kg |
| Total Weight | 9700 kg |
| Outline Dimensions（L×W×H）in. | 2880×2200×2100（mm） |
| Lifting Lug | ELSP Fuse |
| Hinged Door | BAY-O-NET Fuse |
| Parking Bracket | Tap Changer |
| Tank Cover | Oil Level Gauge |
| L.V Bushing (4-Hole ) | Pressure Relief Valve |
| Two/Four Position Load break Switch | Vacuum Pressure Gauge |
| HV Grounding Copper Bar | Terminal Block |
| Temperature Indicator | Door Handle |
| H.V Bushing Well(15kV) | Ground Strap |
| Grounding Copper Bar | Nameplate |
| 1"'Drain Valve With 3/8" Sampler | IR Window |
| 1" Upper Fill Valve Filter Press Connection | Terminal Box |
| Non-PCB decal | High Voltage Warning Signs |
Customization Optional
3750kVA Three Phase Pad Mounted Transformer
The 3750kVA three-phase pad mounted transformer provides extensive customization to accommodate specific voltage classes, protection needs, environmental challenges, and operational demands while maintaining full compliance with IEEE, ANSI, DOE, and CSA standards. Primary voltages range from 4.16kV to 34.5kV (common: 12.47GrdY/7.2kV, 13.8kV Delta, 24.94GrdY/14.4kV, 34.5GrdY/19.92kV), with secondary outputs like 480Y/277V, 4160Y/2400V, 600Y/347V, or custom configurations. Feed arrangements include radial or loop with dead-front (600A deadbreak bushings) or live-front setups, and winding selections offer aluminum for cost-effective performance or copper for enhanced conductivity, lower hotspots, and superior short-circuit strength. Specialized enhancements encompass FR3 natural ester fluid for fire safety (high flash/fire point, FM Approved), K-factor designs (K-13/K-19) to handle harmonic-rich loads from data centers or variable drives, vacuum fault interrupters (VFI) with visible break, bayonet fuses paired with current-limiting fuses, or differential protection relays.
Enclosure modifications include full stainless steel construction for harsh coastal/industrial corrosion resistance, seismic bracing per IBC requirements, nitrogen preservation systems to minimize oil degradation, or forced air cooling fans (KNAN/ONAF) for increased overload capacity. Additional provisions feature external lockable gauge boxes, surge arresters, CT/PT metering packages, remote SCADA monitoring interfaces, or special coatings/paints for extreme environments. All custom features ensure optimized impedance (5.75–6.5%), BIL levels, efficiency verification, and reduced footprint for tight substation sites, enabling tailored solutions that enhance safety, reliability, and cost-efficiency for large utility expansions, renewable interconnections, or heavy industrial operations.
Packing and Shipping
3750kVA Three Phase Pad Mounted Transformer
The 3750kVA three-phase pad mounted transformer undergoes rigorous packaging to ensure safe arrival despite its substantial size and weight (typically 12,000–16,000kg). The complete assembled unit—tank, compartmental cabinet, bushings, gauges, and accessories—is secured on a reinforced, export-grade wooden skid or pallet base treated per ISPM-15 standards, enabling safe forklift, crane, or roller movement during loading/unloading. All exposed components, including bushings, tap changer handle, and external valves, are protected with padded caps, foam inserts, and temporary bracing to prevent vibration-induced damage.
For international or extended transport, the transformer is enclosed in heavy-duty wooden crates or open-top cases with internal cross-bracing, shock-absorbing materials, and anti-tilt restraints to handle sea, rail, or road dynamics. Oil-filled units ship under vacuum or nitrogen blanket to preserve insulation integrity and avoid moisture; any additional fluid is packed in sealed, absorbent-lined drums within separate crates. Sensitive elements like pressure relief devices and gauges receive extra padding and shockproof wrapping.
Domestic North American shipments utilize specialized heavy-haul flatbed or lowboy trailers with multi-point chain tie-downs, load spreaders, and blocking compliant with DOT/OSHA regulations; oversize loads (approx. dimensions 3m L × 2.5m W × 2.5m H) often require pilot/escort vehicles and route permits. International ocean transport employs 40ft+ flat-rack or open-top containers on RoRo ships, secured with IMO-standard lashings, chocks, and weather protection. Inland portions use air-ride trailers to reduce road shocks. Full cargo insurance, real-time GPS tracking, and complete export documentation (packing lists, bills of lading, test certificates, customs declarations) accompany every shipment.
Upon delivery, a thorough visual and mechanical inspection checks for transit issues, with prompt reporting for warranty claims. These comprehensive packing and shipping measures protect against mechanical stress, environmental exposure, or contamination, guaranteeing the transformer reaches the site in optimal condition for immediate, long-term reliable service in high-demand applications.
For international or extended transport, the transformer is enclosed in heavy-duty wooden crates or open-top cases with internal cross-bracing, shock-absorbing materials, and anti-tilt restraints to handle sea, rail, or road dynamics. Oil-filled units ship under vacuum or nitrogen blanket to preserve insulation integrity and avoid moisture; any additional fluid is packed in sealed, absorbent-lined drums within separate crates. Sensitive elements like pressure relief devices and gauges receive extra padding and shockproof wrapping.
Domestic North American shipments utilize specialized heavy-haul flatbed or lowboy trailers with multi-point chain tie-downs, load spreaders, and blocking compliant with DOT/OSHA regulations; oversize loads (approx. dimensions 3m L × 2.5m W × 2.5m H) often require pilot/escort vehicles and route permits. International ocean transport employs 40ft+ flat-rack or open-top containers on RoRo ships, secured with IMO-standard lashings, chocks, and weather protection. Inland portions use air-ride trailers to reduce road shocks. Full cargo insurance, real-time GPS tracking, and complete export documentation (packing lists, bills of lading, test certificates, customs declarations) accompany every shipment.
Upon delivery, a thorough visual and mechanical inspection checks for transit issues, with prompt reporting for warranty claims. These comprehensive packing and shipping measures protect against mechanical stress, environmental exposure, or contamination, guaranteeing the transformer reaches the site in optimal condition for immediate, long-term reliable service in high-demand applications.
32
32 years of industry experience
Manufacturer Test
3750kVA Three Phase Pad Mounted Transformer
Progress test
The initial progress test phase for the 3750kVA pad mounted transformer (per IEEE C57.12.90 routines during core/coil fabrication) verifies essential electrical and structural integrity before oil filling and enclosure finalization. Winding resistance is measured DC across all phases/taps at ambient, corrected to 75°C, limiting variation to ≤2% for detecting joint faults or conductor inconsistencies. Turns ratio and polarity/phase relation tests use precision TTR on every tap, ensuring ≤±0.5% match to nameplate and accurate vector group. Pre-fill oil dielectric checks include breakdown (>35kV/2.5mm), moisture (<10ppm), and dissipation factor. Tank leak test via pressure/vacuum/helium confirms hermetic seal. Tap changer, gauge, and accessory functions are operationally confirmed. These early validations catch defects promptly, ensuring progression with solid baseline data and compliance documentation.
Design Tests
All transformers will be tested after finishing the production, test items as follows:
♦ Insulation Power Factor
♦ Ratio, Polarity, and Phase Relation
♦ Winding Resistance
♦ Impulse Tests
♦ On load Loss Test
♦ No Load Loss Test
♦ Leak Test
♦ DC Insulation Resistance Test
♦ Transformer Turns Ratio/TTR (All Tap Voltages)
♦ Impedance Voltage & Load Loss (Rated Voltage)
♦ Polarity, 1-Ph / Phase Relation, 3-Ph (Rated Voltage)
♦ Excitation & No-Load Loss (Rated Voltage)
♦ Insulation Resistance (Rated Voltage)
♦ Temperature Rise
♦ Dielectric Withstand (Hipot)
Transformer Factory Acceptance Test
Extended FAT routines emphasize load, dielectric, and compatibility for the 3750kVA pad mounted transformer. Load loss/impedance short-circuit test measures copper losses (reference temperature-corrected) and percent impedance (5.75–6.0%) ensuring efficiency/fault limits. Applied voltage withstand confirms main insulation integrity to ground/between windings. Routine impulse test (reduced/full waves) validates BIL (95–150kV) with waveform analysis. Zero-sequence impedance supports relay settings if specified. Control/protection functions test gauges, relief device, and tap changer for accurate response. Final visual/mechanical inspection verifies ANSI C57.12.28 tamper-proof enclosure, paint/coating, bushing/terminal setup, grounding, and nameplate. Total losses/efficiency cross-check against guarantees.
Routine Test - Transformer Turns Ratio/TTR (All Tap Voltages)
Purpose of Testing
The purpose of the transformer turns ratio (TTR) test is to confirm whether the voltage ratio between each tap of the transformer meets the design requirements and ensure that the transformer winding is connected correctly. By measuring the voltage ratio of each tap, it is possible to detect whether there is a fault or deviation in the transformer winding.
Testing Equipment
TTR tester: such as Doble, Megger, Omicron and other brands of transformer winding ratio tester.
Voltage source: usually AC 10 V to 30 V , used to test different voltages for each tap.
Temperature and humidity meter: used to record environmental conditions during the test to ensure test accuracy.
Current probe: used to measure the load current of the winding and ensure the accuracy of the test results.
Voltage source: usually AC 10 V to 30 V , used to test different voltages for each tap.
Temperature and humidity meter: used to record environmental conditions during the test to ensure test accuracy.
Current probe: used to measure the load current of the winding and ensure the accuracy of the test results.
Pre-Test Preparation
Disconnect all transformer tap-changers from the power supply and ensure that all equipment is properly grounded and discharged.
Perform the test under suitable environmental conditions: relative humidity below 75% and no rain (recommended temperature: 20-30°C). Avoid high humidity or bad weather that may affect the test accuracy.
Perform the test under suitable environmental conditions: relative humidity below 75% and no rain (recommended temperature: 20-30°C). Avoid high humidity or bad weather that may affect the test accuracy.
Test Progress
Perform the test under suitable environmental conditions: relative humidity below 75% and no rain (recommended temperature: 20-30°C). Avoid high humidity or bad weather that may affect the test accuracy.
Measure and Record
Start the test and record the following parameters:
The voltage ratio between the windings
Deviation of the measured value from the rated ratio
The voltage ratio between the windings
Deviation of the measured value from the rated ratio
Temperature Correction
If necessary, perform temperature correction on the measured turns ratio data (especially when testing at higher or lower temperatures). Generally, the standard reference temperature for temperature correction is 20°C.
Repeat Testing (if necessary)
Test the transformer's windings of different voltage levels (high voltage, medium voltage, and low voltage) separately to ensure that the turns ratios of all windings are normal.
Evaluation Criteria (Reference)
Turns ratio error ≤ 0.5% (pass)
0.5% < Turns ratio error ≤ 1% (caution)
Turns ratio error > 1% (further inspection or corrective action required)
0.5% < Turns ratio error ≤ 1% (caution)
Turns ratio error > 1% (further inspection or corrective action required)
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
The 3750kVA three-phase pad mounted transformer excels in large utility substations, heavy industrial plants like manufacturing facilities and mining operations, and expansive commercial complexes such as warehouses or distribution centers. It combines effectively with renewable energy farms (solar/wind step-up), large-scale EV charging infrastructure, and data center power backups for high-reliability, underground medium-voltage distribution in demanding urban or remote settings.
Technical Advantages
● 30+ years of manufacturing experience
● ISO and UL certified production
● Customized cable and transformer solutions
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What is a Transformer?A transformer is an electrical device used to change the voltage of alternating current (AC). It works on the principle of electromagnetic induction, converting high-voltage current into low-voltage current or low-voltage current into high-voltage current. Transformers are widely used in power transmission, distribution systems, and various electronic devices.
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What are the main uses of a transformer?The main use of a transformer is voltage conversion. Transformers are used in power transmission systems to help transfer electricity from power plants to consumers. In addition, transformers are also used in electronic devices such as chargers, televisions, power adapters, etc., to adjust the voltage to meet the requirements of different devices.
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Do you have UL listed?Yes, our transformer has UL listed. We have exported to America many pad mounted transformer,substation transformer and HV.
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