Three-phase pad-mounted transformer

Medium-voltage transformers

Eaton’s Cooper Power series three-phase pad-mounted transformers are compact power centers for utility, commercial or industrial applications, designed to withstand many types of environments. These transformers can be located outside or inside buildings to offer an energy efficient and safer solution. Fluid-filled transformers are available in a wide variety of configurations and can be paired with a large selection of accessories to meet the most basic and the most complex of specifications.

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Three-phase pad-mounted compartmental type transformer catalog Three-phase pad-mounted compartmental type transformer installation and maintenance instructions

Overview Technical Resources Support

Base rating

45-12,000 kVA

Primary voltage

2400-38,000 V

Secondary voltage

208Y/120 V to 24,940 V

Core features

Compartmental available in live-front or dead-front design
Critical load designed with special attention to surge protection
Hardened data center designed with special attention to surge protection, providing superior performance under the most stressful electrical environments
Solar specifically designed for Solar Photovoltaic generator step-up (GSU) applications
Vacuum fault interrupter combines both voltage transformation and either transformer or loop overcurrent protection in one space-saving, money-saving package
Can be located near or inside buildings for greater flexibility and savings

The safe, reliable, environmentally friendly choice

Utilizing FR3 high-fire-point dielectric fluid, the liquid-filled transformers enhance fire safety while providing environmental benefits and increasing equipment longevity. FR3 fluid is readily biodegradable, non-toxic and provides sustainable performance at a low cost. Mineral oil and other alternative fluids are also available.

Designed to withstand all environmental hazards

Eaton's Cooper Power series three-phase pad-mounted transformers are constructed with unparalleled quality and coated with proven E-coat technology — meeting or exceeding all applicable ANSI, NEMA, IEEE and CSA standards, as well as NEC and CEA specifications. In addition, full UL listing and FM approval are available up to 35kV.

Customized transformers to meet every need

Offering a multitude of configurations and accessories to meet a wide range of application demands, Eaton's Cooper Power series three-phase pad-mount transformers are engineered-to-order and manufactured to exact customer specifications. Some models from stock are also available for emergency situations.

Specifications

Ratings

Base kVA	45 kVA to 12,000 kVA
Primary voltage	2400 V to 38,000 V
Secondary voltage	120 V to 24,940 V
Basic Impulse Level (BIL)	30kV to 250kV

Standards

ANSI/IEEE	C57.12.00 and C57.12.34
CSA	C227.4
NEMA (sound level)	NEMA TR-1
Third-party approval/recognition	FM Global (Indoor & Outdoor), UL/cUL – available for most ratings

Enclosure

Layout	Compartmental type
Tamper resistance	Three-point latching and padlock system with recessed penta-head bolts
Enclosure integrity	Meets or exceeds ANSI/IEEE C57.12.28 and C57.12.29 (if stainless construction)
Material	Mild or stainless steel (304L)
Enclosure environment	Indoor and outdoor
Insulating medium	Air

Key features

Distribution transformer	Three-phase pad-mounted
Install location	Indoor and outdoor
Power direction	Step-down and step-up

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Brochures

Commercial and industrial medium-voltage electrical distribution products brochure

This brochure outlines Eaton’s Cooper Power series broad commercial and industrial medium-voltage transformer, switchgear, fuse, sectionalizer, switch, regulator, tool, OEM equipment, cable accessory, lightning arrester, power capacitor and recloser offerings.

(PDF 2 MB , 01/24/2023)

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External visible loadbreak option for medium-voltage transformers product aid

This brochure describes Eaton’s Cooper Power series external visible loadbreak option which offers easy access to verify isolation of internal transformer circuitry without exposure to the risk of dangerous arc flash in the low-voltage transformer compartment.

(PDF 186 KB , 09/01/2017)

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Transformer solutions to reduce arc flash exposure product aid

This brochure explains that Eaton’s Cooper Power series can reduce maintenance and operating costs while providing improved safety by minimizing exposure to potential arc flash.

(PDF 872 KB , 09/01/2015)

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Catalogs

Three-phase pad-mounted compartmental type transformer

This catalog provides features and ordering information for Eaton’s Cooper Power series three-phase pad-mounted compartmental types transformers available with electrical grade mineral oil or Envirotemp FR3 fluid, a less-flammable and bio-degradable fluid.

(PDF 446 KB , 02/19/2025)

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Installation instructions

2020 NEC Requirement Guidelines for the Installation of Listed Less-Flammable Liquid-Filled Transformers

These guidelines represent Eaton's understanding and interpretation of the National Electrical Code, UL Classification of Envirotemp FR3 Fluid and FM Global Property Loss Prevention Data Sheets 5-4 - Transformers, Approved Transformer Fluids Standard 6933, FM Approved Transformer Standard 3990 and IEEE standards in effect at the time of this publication. It does not necessarily represent the position of Eaton on the protection and installation of less-flammable transformers.

(PDF 570 KB , 10/10/2021)

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Three-phase pad-mounted compartmental type transformer installation and maintenance instructions

These instructions have been prepared to assist qualified technicians in the installation, operation and service of Eaton's Cooper Power series three-phase pad-mounted compartmental type transformers.

(PDF 1 MB , 08/01/2015)

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Product specification guides

Functional specification for three-phase pad-mounted distribution transformers 45–10,000 kVA

This specification covers the electrical and mechanical characteristics of Eaton’s Cooper Power series 45-10,000 kVA three-phase step-down pad-mounted distribution transformers.

(DOC 484 KB , 04/03/2025)

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Liquid-filled, medium-voltage AR-VFI pad-mounted transformer specification

This is a CSI formatted construction guide specification for liquid-filled, medium-voltage AR-VFI pad-mounted transformers.

(DOCX 328 KB , 02/13/2025)

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Liquid-filled, medium-voltage pad-mounted transformer specification

This is a CSI formatted construction guide specification for liquid-filled, medium-voltage pad-mounted transformers.

(DOCX 315 KB , 02/13/2025)

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Liquid-filled, medium-voltage pad-mounted transformer specification (CSA)

This is a CSI formatted construction guide specification for liquid-filled, medium-voltage pad-mounted transformers (CSA version).

(DOCX 319 KB , 02/13/2025)

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Liquid-filled, medium-voltage S-VFI pad-mounted transformer specification

This is a CSI formatted construction guide specification for liquid-filled, medium-voltage S-VFI pad-mounted transformers.

(DOCX 327 KB , 02/13/2025)

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Technical data sheets

Bay-O-Net with ELSP fuse vs. drywell canister fusing information

This document provides Bay-O-Net with ELSP fuse vs. drywell canister fusing information.

(PDF 47 KB , 09/01/2016)

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Copper vs. aluminum conductor information

This document provides cooper vs. aluminum conductor information.

(PDF 54 KB , 09/01/2016)

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Distribution transformers mineral oil-immersed, self-cooled, 60 Hertz voltages and connections information

This document provides distribution transformer mineral oil-immersed, self-cooled, 60 Hertz voltages and connections information.

(PDF 196 KB , 10/01/2016)

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Overvoltage protection for pad-mounted transformers information

This document discusses how understanding the different arrester types and duty cycles available can greatly reduce the risk of losing a transformer due to an overvoltage, while minimizing the cost of overvoltage protection.

(PDF 72 KB , 09/01/2016)

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Pad-mounted transformer fusing philosophies

The fusing philosophies described in this document have been used for many years to create fuse selection and coordination tables for Eaton's Cooper Power series fuses used in pad-mounted transformer applications.

(PDF 117 KB , 06/01/2023)

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Rectangular vs. round coils information

This document provides rectangular vs. round coils information.

(PDF 69 KB , 09/01/2016)

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VFI transformer vs. switchgear information

This technical document discusses how a transformer equipped with an integral vacuum fault interrupter (VFI) can be an alternative to a non-VFI transformer in combination with stand-alone switchgear.

(PDF 57 KB , 03/01/2015)

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When to use a three-phase pad-mounted transformer

This document describes why in an underground primary feeder system, three-phase pad-mounted transformers are an alternative to three-phase substation transformers.

(PDF 49 KB , 03/01/2015)

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White papers

Proper evaluation of power factor in rectangular and circular coil small power transformer designs white paper

This paper will explore the differences between rectangular and circular coil designs as they relate to power factor and establish acceptable values for each.

(PDF 214 KB , 05/28/2021)

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Product advisory

Learn about the fundamentals of medium-voltage transformers

Learn more

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Contact and process information

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Phone

877-277-4636 or 877-ETN-CARE

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Eaton is an intelligent power management company dedicated to improving the quality of life and protecting the environment for people everywhere. We are guided by our commitment to do business right, to operate sustainably and to help our customers manage power ─ today and well into the future. By capitalizing on the global growth trends of electrification and digitalization, we’re accelerating the planet’s transition to renewable energy and helping to solve the world’s most urgent power management challenges.

Three-phase pad-mounted transformer

Core features

The safe, reliable, environmentally friendly choice

Designed to withstand all environmental hazards