Medium Voltage
Dry-Type Transformers

Unit substation dry-type transformers are designed for medium voltage power distribution where liquid-cooling is not an option, such as indoor power distribution line-ups, or outdoor areas with environmental concerns.

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A maddox medium voltage dry-type transformer

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Maddox medium voltage dry-type transformer

Maddox medium voltage dry-type with front panel removed

Bus bar on a Maddox medium voltage dry-type transformer

Core and coil of a Maddox medium voltage dry-type transformer

Taps on a Maddox medium voltage dry-type transformer

Hardware and warning label on a Maddox medium voltage dry-type transformer

Transformer Specifications

kVA: 300 – 5,000 kVA

Maddox medium voltage dry-types are designed, built, and tested in accordance with the highest industry standards including NEMA, ANSI C.57, DOE, and IEEE as applicable. They can be configured for general purpose and unit substation applications and are customizable to give you greater control over your unit’s function and safety.

Voltage: up to 35 kV

Standard Features

Self-cooled (AA)
Aluminum windings
Voltage adjustment taps
Impedance 5.75 % (±7.5%)
NEMA 1 indoor enclosure
High-grade silicon-steel core
Ground pads/lugs
150 degree C rise
VPI windings
Stub-up/down bus
Stainless steel hardware

Optional Upgrades

Forced air cooling system (AA/FA)
Copper windings
NEMA 3R outdoor enclosure
Lightning arresters
80 C or 115 C degree rise
Solar step-up design
Electrostatic shielding
K-rated design
Cast-coil windings
Bus to ends
Transition section/terminal chambers
Temperature monitoring system
Primary load-interrupter switch
Double-thick varnish for corrosion protection

Available Certifications

Maddox MV dry type transformers are available with UL, CSA, or ETL certifications.

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3 Year Warranty

Backed by US-based support

USA Options

Made-in-America available

Hit Your Lead Time with Stock and Custom Options

Maddox keeps medium voltage dry-type transformers in stock for fast deliveries and builds custom ones with some of the best lead times in the industry.

Stock

Hit project deadlines with common kVA sizes and voltages, in stock and ready to ship.

Custom

Build exactly what you need with extensive transformer customizations available.

Projects Powered by Maddox Substations

Maddox dry type transformers provide reliable power to critical projects across the United States.

Competitive pricing, always the most inventory, and exceptional after sales support. They are my "go to" option for transformers

David D.

This is my 5th order from Maddox. Always knowledgeable and helpful. Every transformer I have purchased has worked perfectly.

Jason W.

They have stock when others don't and are quick to ship and fill their orders. VERY THANKFUL we found them.

Mike A.

The transformer I ordered was delivered onsite at our project in two business days. Great service!

Jerome T.

Great company easy to deal with. Every transformer I buy will be from Maddox.

Austin M.

First time purchasing from Maddox. Was very easy and we are pleased with the results of our purchase.

Chris O.

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Fill out the form and we will get back to you as soon as possible. Our average response time during business hours is 30 minutes.

Meet Any Spec with Extensive Customizations

Meet your exact spec with customized transformers designed, built, and tested in accordance with the highest industry standards including NEMA, ANSI, DOE, and IEEE as applicable.

High-Grade
Silicon-Steel Core

Improve efficiency while keeping losses and operating noise lower under normal and heavy load conditions.

Copper or
Aluminum Windings

Choose the winding material that meets your spec and budget, achieving dependable performance and service life with either option.

VPI or Cast-Coil
Windings

Select the insulation system that fits your environment—VPI for enhanced moisture resistance or cast-coil for maximum protection in harsh, high-contaminant conditions.

Frequently Asked Questions

Does my application require a low or medium voltage dry-type transformer?

General purpose low voltage dry-type transformers are suitable for applications requiring 800 volts or less. All other applications will require a Maddox medium voltage dry-type transformer.

Do Maddox medium voltage dry-type transformers use cast coil or VPI windings?

While standard designs use VPI windings, cast coil windings are available upon request. Learn more about cast coil transformers here.

How can I clean my dry-type transformer to prevent performance issues?

We recommend cleaning the windings, insulating surfaces, connections, and vent filters on an annual basis. Learn how to clean your dry-type transformer here.

What types of enclosures are available for Maddox medium voltage dry-type transformers?

While standard designs use NEMA 1 enclosures, additional NEMA ratings are available upon request for applications that require increased protection. Learn about the types of transformer enclosures here.

Are Maddox medium voltage dry-type transformers K-factor rated?

While standard designs do not feature K-factor rated components, these are available upon request for applications that require protection against harmonics. Learn about K-factor rated transformers here.

Do Maddox medium voltage dry-type transformers feature electrostatic shields?

While standard designs do not feature electrostatic shields (e-shields), these are available upon request for applications that require higher tolerances for voltage disturbances. Learn about e-shields here.

Which cooling class do Maddox medium voltage dry-type transformers feature?

While standard designs feature ventilated self-cooled ratings (AA), additional cooling classes are available upon request. Learn about transformer cooling classes here.

Can Maddox close couple dry-type transformers with switchgear?

Yes, Maddox can close couple metal-enclosed switchgear to a medium voltage dry-type transformer upon request. Learn more about switchgear and close coupled designs here.

Are Maddox remanufactured medium voltage dry-type transformers reliable?

Yes, Maddox remanufactured medium voltage dry-type transformers are tested in accordance with NEMA, ANSI, DOE, and IEEE standards as applicable. Learn about remanufactured transformers here.

Can I return or exchange a Maddox medium voltage dry-type transformer?

Yes, medium voltage dry-type transformers may be eligible for return or exchange within six months of shipment date. Terms and conditions apply. Learn about the Maddox return and exchange policy here.

Medium Voltage
Dry-Type Transformers