Unit Substation Dry Type

Product Range

Three Phase

Voltage Class

  • 600 V thru 1.2 kV
  • 2.4 kV thru 5 kV
  • 8.7 kV thru 15 kV
  • 25 kV
  • 34.5 kV


  • 9 thru 2,000
  • 15 thru 10,000
  • 45 thru 10,000
  • 225 thru 10,000
  • 500 thru 10,000

Single Phase

Voltage Class

  • 600 V thru 1.2 kV
  • 2.4 kV thru 5 kV
  • 8.7 kV thru 15 kV
  • 25 kV
  • 34.5 kV


  • 10 thru 833
  • 15 thru 1,667
  • 30 thru 3,333
  • 150 thru 6,667
  • 333 thru 6,667


  • Aluminum/Copper
  • 150°C / 115°C / 80°C or Special Request
  • 220°C insulation
  • NEMA standard/special sound levels
  • ANSI standard/special BIL levels
  • VPI
  • UL K-factor ratings
  • UL/CUL/CE/CSA listings (check with factory)
  • Multi-voltage input/output
  • 50/60/400 Hz
  • OEM core and coil
  • Multiple electrostatic shields
  • Design to meet customer impedance and loss criteria

For over four decades, MGM Transformer Company has been a reliable source for quality secondary unit substation transformers. Our standard designs cover the full range of requirements from 5kV to 34.5kV, 500kVA to 10,000kVA, in both liquid and dry type. As an engineering oriented transformer company, we maintain a large engineering staff. Our experience in working with various switchgear manufacturers enables us to design the high voltage/low voltage switchgear interface, assuring the proper match in the field. Flex connectors can be supplied. Non-standard substation designs are also available for special situations such as failed unit retrofitting or PCB replacement. All manufacturing processes are done on the premises.This advantage, along with
a large inventory of electrical steel and wire, assures our customers of the industry’s shortest standard lead times, regardless of the interface

Safe, Convenient and Environmentally Sound

Installations of ventilated dry-type transformers do not require a liquid confinement area, automatic fire extinguishing system or fire vault. Drytype transformers use no insulating liquids, virtually eliminating the risk of local environment contamination and simplifying routine maintenance by eliminating the need to check, replace or clean liquid. Dry-type units are relatively lightweight and can be conveniently installed on upper floors, balconies, roof trusses or roofs. Insurance companies generally offer lower premiums for installations of dry-types than for liquid-filled transformers.

General Construction

Coils are vacuum-pressureimpregnated (VPI) with solventless polyester resin, ensuring complete impregnation of the windings and insulation.The finished VPI coils are incredibly strong, readily dissipate heat and are protected against moisture, dirt and most industrial contaminants. Ventilated dry-type winding designs vary depending on the voltage, basic impulse level (BIL) and current of the individual winding and/or application of the transformer. For all units, the insulation system will be 220°C regardless of the average winding rise.

MGM ventilated dry-type transformers are designed for indoor or outdoor applications in schools, hospitals, industrial plants, commercial buildings and any place requiring safe and dependable power.Ventilated dry-type transformers offer an economical solution and are extremely reliable when properly installed and maintained.


The standard indoor enclosure is NEMA 1, Category C construction. Enclosures are suitable for lifting, jacking, rolling or skidding with provisions for lifting from the transformer base. High voltage and low voltage ANSI ground pads are provided.

The enclosure paint finish is neat, clean and highly resistant to corrosion. Metal surfaces are thoroughly cleaned of scale, oil, grease, rust and other foreign matter before painting. Unless specified otherwise, paint color shall be ANSI 61 (light gray). NEMA 3R outdoor enclosures are available for applications that prohibit indoor installation.


Generally, low voltage (LV) windings less than 2,400 volts are either multi-conductor barrel or sheet conductor types. Multi-conductor windings may be more economical and preferred in smaller kVA low voltage applications in which the current and axial short circuit forces are relatively small. High voltage (HV) windings 2,400 volts or greater may be single-section barrel, multi-section barrel or disk types. Ventilated drytype coils may be either round or rectangular through about 2,000 kVA. Transformers larger than 2,000 kVA generally are designed with round windings unless there are special considerations, such as limiting dimensions.


The transformer cores are constructed of non-aging, high grade, grain oriented silicon steel laminations with high magnetic permeability. Magnetic flux densities are kept well below the saturation point. Core laminations are free of burrs and stacked without gaps. Mitered construction cores may be provided when specified. The core clamping brackets are designed to provide even distribution of clamping forces to the core yokes and legs. The core is electrically isolated except for the factory-installed core ground strap, which provides a single path from the core to ground.


All units rated 750 kVA and higher can have added fans, increasing capacity in all current carrying parts for the fan-cooled rating and capability to add a thermometer relay to control fans. When specified, the transformer shall be provided with fans to give a forced air-cooled rating of 33% above the self-cooled rating. Control wiring (wire markers included), a thermal sensor and a fan controller will be supplied.

Standard Features

  • UL Listing, CSA, & CUL
  • Vacuum Pressure Impregnated (VPI) windings
  • 80°, 115°, 150°C average winding rise ratings
  • 60 Hz operation
  • 220°C insulation system
  • Aluminum or copper windings
  • ANSI ground pads
  • Core ground strap
  • Indoor ventilated enclosure – NEMA 1
  • Paint — ANSI 61 finish
  • Provisions for lifting
  • Removable front and rear panels
  • Vibration isolating pads
  • (2) 2 1/2 % full capacity taps above and below nominal
  • Conform to NEMA, ANSI, & IEE standards for Dry Type Transformers
  • Seismic Zone IV


  • Fans for 133% FA kVA rating
  • Future fan wiring and control
  • Ground bus – full length copper
  • Impact indicator – Mechanical
  • Outdoor enclosure NEMA 3R
  • Paint — polyurethane overcoat
  • Screened ventilation openings
  • Enclosure — hinged panels
  • Enclosure — knockdown
  • Space heaters
  • Temperature monitor/fan controller
  • Thermostat for space heaters
  • Bus to End
  • Flex Leads
  • Low Noise


The transformer shall be designed to meet or exceed ANSI and NEMA sound levels for dry-type transformers. As an option, transformers designed at -3dB below ANSI and NEMA standard sound levels are available.

Test results, when requested, are available by transformer serial number. In addition, the following special tests can be performed on each transformer
in accordance with applicable ANSI standards at an additional cost.

  • Temperature test
  • Impulse test
  • Sound test
  • Insulation power factor test
  • Partial discharge test

Product Coordination

When specified, transformers can be closecoupled to a multitude of High Voltage and Low Voltage Switchgear.


Each transformer shall receive the following standard production tests in accordance with ANSI C57.12.90

  • Resistance test
  • Polarity & phase relation test
  • Turns ration test
  • No-load loss & exiting current test
  • Impedance and load-loss test
  • Applied potential test
  • Induced potential test

Special Design or Application

  • Low loss designs
  • Rectifier transformer designs
  • Special ambient designs
  • High overload capacity designs
  • Special/low sound level designs
  • 50 Hz designs
  • Series/parallel windings
  • Retrofit to specific dimensions
  • K-factor ratings
  • Special Paint
  • Auto transformers
  • PCB replacement

Vent Dry Basic Impulse Rating

Vent Dry Sound Level

Single Phase Dry Type

Three Phase Dry Type

Bull Rush Program


Need it fast? We can deliver.  Emergencies happen and we can expedite the manufacturing of your units to meet your delivery requirements.  Ask about our Bull Rush program when you place your order and we can manufacture and ship your unit in as fast as 5 working days!


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“Buy U.S.” Statutes


MGM Transformer Company can manufacture your units at our 120,000 square foot plant in the U.S. and source the raw materials solely from American companies if required. By doing so we can certify your units to be compliant with any of the various “Buy U.S.” statutes listed below (either state or federal). Please make sure to specify your requirements at the time of order.


  • Made in USA
  • ARRA (American Recovery and Reinvestment Act)
  • BAA (Buy American Act & Buy America Provisions)
  • TAA (Trade Agreements Act)
  • SPPA 73 P.S. 1881  (Steel Products Procurement Act)