Transformer types and project fit
J&J Transformers LLC is a power transformer supplier serving utilities, data centers, EPCs and industrial projects nationwide. Browse GSU, substation, step-down and pad-mounted transformers by voltage and capacity. Need another configuration? Send Tommy Marco your kVA or MVA, voltages, quantity and required date. Each offered unit requires engineering review and written availability confirmation; subject to prior sale.
J&J Transformers LLC · Sugar Land, Texas · Serving projects nationwide
Tommy Marco · tommy@jjtransformers.com
Current transformer listings
Start with the public ratings below. Call or email Tommy for current availability, pricing, photos and the technical package. Each unit needs project-specific engineering review and remains subject to prior sale.
Technical records reviewed
Email for Specs, Price & AvailabilityTechnical records reviewed
Email for Specs, Price & AvailabilityTechnical records reviewed
Email for Specs, Price & AvailabilityTechnical records reviewed
Email for Specs, Price & AvailabilityJ&J supplies large power transformers for U.S. projects. Start with a current listing or call Tommy with a requirement beyond the public inventory. GSU, substation, step-down and pad-mounted equipment follow different project specifications.
| Transformer class | Primary duty | Decision inputs | Next page |
|---|---|---|---|
| Generator step-up (GSU) | Raises generator terminal voltage to a plant or interconnection bus | Generator MVA, voltage, PF/reactive range, high-side voltage, impedance, BIL, GCB arrangement | GSU transformer page |
| Substation / power | Changes voltage between transmission, subtransmission, or campus distribution levels | MVA, HV/LV/tertiary, LTC/DETC, BIL, impedance, losses, cooling, fault duty | Substation transformer page |
| Pad-mounted | Outdoor compartmental distribution close to a load block | kVA, primary/secondary, loop/radial, dead/live front, fusing, switch, fluid, enclosure | Pad-mounted transformer page |
| Dry-type | Indoor or outdoor distribution where the chosen insulation system and enclosure fit the site | kVA/MVA, voltage, BIL, enclosure, ventilation, temperature rise, sound, harmonics, AHJ requirements | Transformer comparison guide |
A matching voltage ratio is the starting point. Compare the existing transformer and proposed replacement on the same rating basis before reserving equipment. Send the nameplate or one-line by email when available; an initial conversation can begin with MVA, voltages and your required date.
| Compare | What the project team needs to confirm |
|---|---|
| Capacity and cooling | Required MVA at each cooling stage, ambient conditions and operating duty—not only the highest rating. |
| Winding connections | High, low and tertiary voltages; vector group, phase displacement, neutral and grounding requirements. |
| System performance | Impedance with its MVA base, tap range and controls, insulation levels, protection and fault-duty requirements. |
| Installation and schedule | Terminal arrangement, dimensions, accessories, inspection, loading, transport and the needed-on-site date. |
Start with capacity, phase, frequency, high- and low-side voltages, duty, site, and needed-on-site date. To confirm a technical match, we may also need BIL, impedance, cooling, vector group, neutral and taps, fluid, losses, harmonics, site conditions, sound limits, and shipping constraints.
We screen requirements in the 69, 115, 138, 161, 230, and 345 kV classes when a source and supporting records are available. Ratios such as 230/34.5, 138/34.5, 230/13.8, 345/34.5, and 230/69 kV are common searches, but the ratio alone never establishes a technical fit.
| HV class | Example search ratios | Project team must confirm |
|---|---|---|
| 69 / 115 kV | 69/13.8 · 115/34.5 | MVA, maximum system voltage, BIL, impedance, vector, taps, duty, site |
| 138 / 161 kV | 138/34.5 · 138/13.8 · project-specific 161 kV ratios | Generator or substation duty, tertiary, grounding, cooling, losses, documents |
| 230 kV | 230/34.5 · 230/13.8 · 230/69 | Complete winding schedule, BIL, impedance basis, OLTC/DETC, terminals, logistics |
| 345 kV | 345/34.5 and project-specific ratios | Collector/grid duty, tertiary, switching cases, transport, tests, project approval |
Examples describe project search patterns, not guaranteed inventory. Review current opportunities or send an equipment request for a written match.
The applicable standard depends on the transformer class, voltage, construction, duty, owner specification, and manufacture date. Current reviews may reference IEEE C57.12.00 general requirements, IEEE C57.12.90 test methods, current class-specific standards, selected IEC 60076 parts, and federal efficiency rules only where the exact equipment falls within their scope.
Applicable standards, listings, tests, and efficiency requirements are confirmed for each quoted unit; naming a standard is not a certification claim.
Routine, design, and special tests are not interchangeable. A page may describe available test categories, but only the certified report or agreed test plan proves what a specific serial number has passed.
Condition labels are the start of diligence, not the conclusion. Procurement should compare serial-specific records, storage and transport history, preservation, missing accessories, inspection access, test scope, warranty provider, field work, freight, and schedule before assigning value to a condition label.
| Condition | Verify | Common risk |
|---|---|---|
| New factory order | Approved specification, drawings, materials, factory milestones, test plan, warranty and delivery term | Interfaces or approvals remain open; factory date is not delivered date |
| Unused surplus | Title/authority, serial, storage, preservation, test status, completeness and warranty transfer | Built for another project; ratio, impedance, vector, terminals or accessories may not fit |
| Used | Service history, DGA/moisture, electrical tests, bushings, leaks, corrosion, loading, faults and transport | Unknown events or no baseline records |
| Reconditioned | Work scope, parts, shop tests, responsible party and warranty | “Reconditioned” may describe very different work scopes |
A quote should identify the exact offered scope and the evidence actually available. J&J requests the nameplate, rating sheet, outline, schematics, test and loss data, fluid information, accessory and spare lists, condition evidence, current location, shipping configuration, Incoterm, warranty provider, availability date, exclusions, and quote validity.
Availability is subject to prior sale, technical review, and written confirmation by J&J Transformers LLC.
Written quotes and supporting records control unit-specific ratings, availability, condition, price, and delivery.
Yes. Email the required MVA or kVA, high- and low-side voltages, quantity and needed-on-site date. J&J reviews additional supply options for the requirement. Supply capability does not establish that a particular configuration is in stock.
No. The high-side voltage class does not identify the low-side or tertiary voltage. Use the exact-ratio pages or the listing's full voltage description, then request the records for that unit.
Call Tommy Marco at 346-276-9540 or email tommy@jjtransformers.com. Specifications, reports, photos and pricing are shared directly after contact, according to the records available for the proposed unit. Availability remains subject to prior sale and written confirmation.
Choose by duty: GSU for generator export, substation/power transformer for network or campus voltage transformation, and pad-mounted for compartmental medium-voltage distribution near loads.
Start with kVA/MVA, high and low voltage, phase, frequency, duty, site, and date; provide BIL, impedance, cooling, vector group, taps, site conditions, and documents when known.
BIL supports insulation coordination. Impedance affects fault current, regulation, reactive behavior, protection, and parallel operation. Both must match the system studies and purchaser specification.
Yes, after its nameplate, one-line, outline, schematics, test data, site conditions, and interface requirements are compared to candidate units.
Yes, J&J can screen a 125 MVA requirement when the project team supplies the complete duty, cooling-stage ratings, high- and low-side voltages, frequency, BIL, impedance basis, vector and grounding, OLTC or DETC requirement, site, condition acceptance, documents, quantity, and project timing. This is a supply capability, not a claim that a matching 125 MVA unit is currently available.
That is an owner and engineering decision based on condition, evidence, tests, remaining-life assessment, warranty, reliability architecture, and project requirements.
No. Standards and efficiency rules vary by transformer class, construction, voltage, duty, jurisdiction, purchaser specification, and manufacture date.
Yes when defined. The written quote should state origin, destination, shipping configuration, mode, permits, Incoterm, unloading boundaries, taxes/tariffs, and exclusions.
Through written confirmation tied to the specific equipment and quote date after ownership, technical, condition, location, scope, and commercial review.
