01 General
1.1 Project description
This project centers on a 1000 kVA three-phase pad-mounted solar duty transformer we built for a customer in the United States. Designed to meet full ANSI standards and filled with FR3 biodegradable insulating oil, the unit comes in a clean powder-coated white finish (RAL 9003). It’s a loop-feed, dead-front design-compact, durable, and very much ready for real outdoor conditions. Although it serves a solar application, it follows many of the same reliability principles we use in our residential transformer line, just scaled up for utility-level performance.
We delivered it in 2025 for a renewable-energy project, and the customer specifically needed a transformer that could keep up with solar-driven load swings, inverter harmonics, and the higher thermal stress that PV systems see during peak generation hours. The 1000 kVA residential transformer operates in a step-up configuration from 480Y/277 V to 33,260 GRDY/19,203 V for U.S. MV feeder interconnection. No extra interface boxes, no complicated adjustments, just a straightforward fit.
1.2 Project Challenges
 | For this solar project, the customer had several challenges: 1. Solar farms don’t run at full load all day-so the transformer must handle cyclical, fluctuating inverter output without overheating. |
1.3 Technical Specification
1000kVA three phase pad mounted transformer specification and data sheet
| Delivered to | America |
| Year | 2025 |
| Type | Three phase pad mount transformer |
| Standard | IEEE |
| Rated Power | 1000KVA |
| Frequency | 60HZ |
| Feed | Loop |
| Front | Dead |
| Phase | three |
| Cooling Type | KNAN |
| Liquid insulant | FR3 Oil |
| Primary Voltage | 33260GrdY/19203V |
| Secondary Voltage | 480Y/277 |
| Vector Group | YNyn0 |
| Winding Material | Aluminum |
| Impedance | 5.75% |
| Efficiency and Losses Standard | DOE 2016 |
| Tap Changer | 4-POSITION LOADBREAK SWITCH |
| Tapping Range | ±2*2.5% |
| No Load Loss | 1300 W |
| On Load Loss | 6940 W |
| Accessories | Standard Configuration |
1.4 Drawings
1000KVA three phase pad mounted transformer dimensions and weight details
02 Our Targeted Solutions
To make this 1000 kVA solar duty transformer truly ready for PV service, we focused on several key engineering decisions-each addressing specific challenges of solar power applications.
2.1 FR3 Bio Oil for Thermal Stability
We chose FR3 oil, not just because it’s biodegradable, but because it handles heat better than standard mineral oil. Solar sites see wide temperature swings and high daytime loads, and FR3 keeps the transformer cooler and the insulation safer. Temperatures stay in check-oil and windings around 65°C, hot spot 80°C-which means the 1000 kVA residential transformer can handle daily PV swings reliably, day in and day out. Lower operating temperature also translates to a longer lifespan, less maintenance, and fewer surprises. |  |
2.2 Aluminum Windings & Low Impedance
 | The aluminum windings are lightweight yet strong, offering excellent conductivity while reducing losses. Combined with a YNyn0 vector group and 5.75% impedance, the transformer delivers stable voltage even under fluctuating inverter loads. It’s essentially designed to smooth out the ups and downs of solar generation, keeping both the grid and local loads happy. |
2.3 DOE 2016-Efficient Losses
We laid out the core and windings carefully to hit DOE 2016 efficiency targets. No-load loss comes in at 1300 W, load loss at 6940 W-so very little energy is wasted during operation. Over months, years even, that adds up. More of the power your solar panels generate actually makes it to the grid, which means the farm is pulling more value out of every kilowatt-hour.
2.4 Dead-Front Loop-Feed Design
Safety was front and center in the design. The dead-front setup keeps everyone away from live parts, while the loop-feed layout makes connecting and switching straightforward. Field crews can work without constantly worrying about accidental shorts or exposed components-especially handy in sites that are accessible to the public or shared with other utilities. |  |
2.5 Enhanced Outdoor Durability
 | These 1000 kVA residential transformers are built to take whatever the outdoors throws at them. The tank and enclosure? Corrosion-resistant, UV-stable, fully sealed. Powder-coated white (RAL 9003) helps reflect sunlight and keep internal temps lower. Rain, sun, humidity-it doesn’t matter. Inside, everything stays protected, running reliably for years. |
2.6 Solar-Ready Protection
Every unit ships with a full protection suite. We’re talking 200A HV bushings, elbow-type surge arresters, a four-position load break switch, plus a clean grounding scheme with isolated H0/X0. Basically, it’s ready to handle surges, lightning strikes, or sudden switching stresses that are common in solar farms-keeping both the transformer and the grid safe.
03 Testing
Testing Standard
IEEE C57.12.00-2021
IEEE Std C57.12.34-2022
IEEE C57.12.90-2021
Routine Test
1. Resistance Measurements
2. Ratio Tests
3. Phase-Relation Test
4. Insulation Resistance Measurement
5. No-Load Losses and No-Load Current
6. Load Losses, Impedance Voltage and Efficiency
7. Applied Voltage Test
8. Induced Voltage Withstand Test
9. Leak Testing with Pressure for Liquid-Immersed Transformers
04 Packing and transportation
