45-7500kVA 35kVThree-Phase Pad-Mounted Transformer (American Box-Type)

The DINGXING Three-Phase Pad-Mounted Transformer (also known as an American Box-Type Transformer or combined transformer) is a new-generation distribution product specially designed for modern power distribution networks, developed by absorbing advanced international technology and design concepts. With a primary voltage class of up to 35 kV, it integrates the transformer, high-voltage load switch and fuse protection in a single compact, fully sealed enclosure.

Its fully sealed, fully insulated structure provides reliable personnel protection, while the compact design occupies only about 1/3 of the footprint of a European-type transformer of the same capacity — flexible and convenient to install, in either ring-network or terminal configurations.

• Fully Sealed, Fully Insulated, Safe to Touch — The integrated enclosure with insulated bushing systems delivers reliable personal-safety protection; dead-front elbow connectors operate with 200 A load current.

• Compact Footprint, Flexible Installation — Only about 1/3 the size of a European-type transformer of equal capacity; works in ring-network or terminal modes with convenient conversion to improve supply reliability.

• High-Efficiency, Low-Loss, Low-Noise Design — Optimized silicon-steel core and winding design achieve low loss, low sound level and strong short-circuit and overload withstand capability.

• Double-Fuse Full-Range Protection — Dual fusing (bayonet with isolation links or current-limiting fuses) provides full-range high-voltage protection; the latest generation includes a phase-proof function.

• Harsh-Environment Durability — The tank receives "three-prevention" anti-corrosion treatment (anti-rain, anti-moisture, anti-salt-fog); carbon-reinforced or stainless steel tank options suit coastal, desert and other severe climates.

• Automation-Ready Options — Optional electrically operated load switch meets distribution-automation requirements; K-factor, step-up and surge-arrester designs are available for special applications.

Standard Ratings & Design Parameters

Operating Voltages — 300 kVA through 1500 kVA

Operating Voltages — 2000 kVA through 7500 kVA

HV Bushing & Fluid Configuration

Switch Options

• 2-Position LBOR Switch

• 4-Position LBOR Switch (V-blade or T-blade)

• 2-Position LBOR Switches

• Electrically operated load switch (optional, for distribution automation)

Fusing Options

• Bayonets with isolation links

• Current-limiting fuses (CLFs)

• Double-fuse full-range protection

Standard Gauge / Accessory Package

• Pressure relief valve

• Pressure vacuum gauge

• Liquid temperature & level gauges

• Drain & sample valve

• Adjustment taps

Construction

• 3-legged or 5-legged core

• Rectangular wound copper or aluminum windings

• Carbon-reinforced or stainless steel tank

• Steel divider between HV and LV cabinets

• Penta-head captive bolt

Optional Design Features & Accessories

• Gauges with contacts

• External drain and sample valve

• Electrostatic shielding

• K-Factor design

• Step-up design

• Surge arresters

• Commercial centers & shopping malls — Compact pad-mounted substations for urban commercial districts.

• Residential communities — Safe, fully insulated units for neighborhood distribution.

• Industrial & mining enterprises — Robust construction with high overload capability.

• Hospitals & schools — Low-noise, personnel-safe operation in public facilities.

• Airports, stations & ports — Harsh-environment versions for transportation infrastructure.

• Subways & urban rail — Compact footprint for space-limited underground installations.

• Renewable energy & microgrids — Step-up and K-factor designs for solar, wind and non-linear loads.

• Eco-sensitive sites — FR3 vegetable-oil fluid option for fire-safety and environmental zones.

Q1. What is a pad-mounted transformer? A pad-mounted transformer is a ground-mounted, fully sealed distribution transformer installed on a concrete pad. Also known as an American box-type transformer, it connects directly to medium-voltage underground distribution cables and is widely used in commercial centers, residential areas and public facilities.

Q2. What capacity range does the DINGXING pad-mounted transformer cover? The series covers 19 base ratings from 45 kVA to 5000 kVA, with primary voltage classes up to 35 kV.

Q3. What is the difference between dead-front and live-front bushings? Dead-front bushings use fully insulated, separable elbow connectors that can be operated safely with 200 A load current, protecting personnel from live parts. Live-front bushings expose terminated conductors and require approach clearances. Both configurations are available, in loop-feed or radial-feed arrangements.

Q4. What fluid options are available? Type II mineral oil for standard applications, or Envirotemp FR3 vegetable-based oil for enhanced fire safety (higher flash point) and environmental friendliness in eco-sensitive installations.

Q5. Can the transformer be used in a ring network? Yes. The unit can operate in a ring network or as a terminal transformer, with convenient conversion between the two modes to improve power supply reliability. Cable connectors operate with 200 A load current.

Q6. What switch options are available? 2-position or 4-position LBOR (load-break oil rotary) switches with V-blade or T-blade, plus 2-position LBOR switches. An electrically operated load switch is optional to meet distribution-automation requirements.

Q7. What standards does the transformer comply with? The transformer is designed and tested to IEEE, DOE, NEMA, IEC and CSA standards, as well as customer-specific requirements.

Q8. What are the impedance guidelines? 300–500 kVA units: 2.8–5.0% nominal. 750–2500 kVA units: 5.75% nominal. For 3000–7500 kVA ratings, consult DINGXING Electric for a custom design.

Need a three-phase pad-mounted transformer for your project? Contact JiangSu Dingxin Electric Co., Ltd. for datasheets, IEEE/CSA type-test reports, OEM/ODM service and competitive pricing.