General Purpose Low Voltage Transformers

A general purpose dry-type transformer is a low-voltage transformer that uses air as its cooling medium instead of oil, making it safe for indoor installation without the need for a containment vault or fire suppression system. It steps voltage up or down within the 600V class to match the power requirements of connected equipment. These transformers are widely used in commercial buildings, schools, hospitals, manufacturing facilities, retail centers, and industrial plants to distribute power reliably from the utility feed to lighting, HVAC systems, motor controls, panel boards, and general electrical loads.

Our stocked general purpose low-voltage transformers are available in ratings from 15 kVA up to 750 kVA for three-phase units, and from 10 kVA up to 100 kVA for single-phase units. Common three-phase sizes include 15, 30, 45, 75, 112.5, 150, 225, 300, 500, and 750 kVA. For projects requiring ratings outside these sizes, MGM also offers custom-engineered builds through their general purpose custom program.

We stock transformers in the most common North American voltage combinations, including 480V to 208/120V three-phase, 480V to 240/120V three-phase, 240V to 208/120V three-phase, 480V delta primary to 480Y/277V three-phase, 208V delta primary to 480Y/277V three-phase, 240V delta primary to 480Y/277V three-phase, 208V delta primary to 120/208V three-phase, and 240X480V to 120/240V single-phase. Custom voltage combinations are available for projects with non-standard requirements.

Both aluminum and copper winding options are available across our stocked product range. For most standard commercial and light industrial applications in controlled indoor environments, aluminum windings are the more common and cost-effective choice. Copper windings are often specified for marine, coastal, or high-humidity environments, or when the project specification explicitly requires copper.

Contact us directly if you are unsure which winding material is appropriate for your specific application and installation conditions.

Our general purpose transformers are available with NEMA 1, 3R, 4, and 4X enclosure ratings. NEMA 1 is a standard ventilated indoor enclosure suitable for clean, dry indoor locations. The standard stocked enclosure on most models is a NEMA 2 rated drip-proof ventilated metal enclosure with natural draft ventilation, which is dual-rated for indoor or outdoor use. NEMA 3R provides protection against rain for outdoor installations. NEMA 4 and 4X provide watertight and corrosion-resistant protection for washdown or harsh outdoor environments, with 4X adding stainless steel construction for chemical or marine applications. Note that 225, 300, and 500 kVA units are indoor-rated as standard and require an optional Weathershield Kit for outdoor installation.

Our general purpose low-voltage transformers are UL 506 and UL 1561 Listed and are DOE 2016 efficiency compliant, meeting the federal minimum efficiency standards for distribution transformers. Seismic certification per ASCE/SEI 7-05 with OSHPD OSP Pre-Approval is standard on all units, making them eligible for installation in California hospitals and other facilities with strict seismic requirements. Sound levels are designed to meet NEMA ST-20 standards. All units go through a rigorous IEEE test plan during production, which includes winding resistance, turns ratio, polarity and phase relation, no-load losses and exciting current, impedance and load loss, and applied potential testing.

Our 600V class transformers come standard with 6 primary voltage taps: 2 taps at 2.5% full capacity above normal (FCAN) and 4 taps at 2.5% full capacity below normal (FCBN). Voltage taps allow the installer to fine-tune the transformer’s output voltage to compensate for variations in the incoming line voltage at the installation site. If the supply voltage runs consistently high or low relative to the nominal rating, the appropriate tap can be selected to bring the secondary output voltage into the correct range for the connected equipment. Tap adjustments are made on the de-energized primary winding and require the transformer to be shut down before any tap position is changed.

We stock these transformers in over 20 major cities across the continental United States, which means most standard configurations can ship quickly without the delays associated with custom manufacturing. For emergency situations where a transformer needs to be sourced and delivered immediately due to a field failure or critical project deadline, our Bull Rush program provides 24/7 emergency production and delivery support with a money-back guarantee.

Yes. While the stocked range covers the most common commercial and industrial applications, we also offer custom-engineered variants for special duty requirements. These include low-noise designs for sound-sensitive environments such as hospitals or offices, marine duty units for high-humidity and salt air environments, solar duty configurations, totally enclosed non-ventilated (TENV) designs for dirty or contaminated environments where ventilation openings are not acceptable, and autotransformer configurations. Custom enclosures, non-standard frequency options including 50 Hz and 50/60 Hz dual-rated, and non-standard voltage combinations are all available through our customization options. Submit a quote with your specifications.