Pad Mount Transformers
Ryan Sales represents JST for every pad mount transformer application, with single-phase units from 15 to 167 kVA and three-phase units from 75 to 5000 kVA at primaries up to 34.5 kV. Both are liquid-filled, UL listed and built in Wytheville, Virginia. We serve utilities, contractors and industrial plants in Texas and Oklahoma and data center projects nationwide.
Send the voltage, ampacity and fault duty. A rep will narrow it down.
JST Power EquipmentSingle-Phase Liquid-Filled Pad Mounted TransformerCompact single-phase liquid-filled pad mount transformer for underground residential and commercial distribution.- Maximum voltage
- Up to 34.5 kV
- kVA range
- 15–167 kVA
- Phases
- Single-phase
JST Power EquipmentThree-Phase Liquid-Filled Pad Mounted TransformerThree-phase liquid-filled pad mount transformer serving underground commercial, industrial, and utility distribution loads.- Maximum voltage
- Up to 34.5 kV
- kVA range
- 75–5000 kVA
- Phases
- Three-phase
How to choose pad mount transformers
Single-phase or three-phase
The load decides this one: residential and light commercial underground service runs on single-phase, while motors, large HVAC and data center loads need three-phase. The Single-Phase Liquid-Filled Pad Mounted Transformer is the compact choice for subdivisions and small commercial services. The Three-Phase Liquid-Filled Pad Mounted Transformer serves commercial, industrial, hospital, private utility and data center loads.
| Model | Phases | kVA range | Primary voltage | Design |
|---|---|---|---|---|
| JST Single-Phase Pad Mount | 1 | 15 to 167 kVA | Up to 34.5 kV | Compartment type, loop or radial feed |
| JST Three-Phase Pad Mount | 3 | 75 to 5000 kVA | Up to 34.5 kV | Dead-front compartment |
Size the kVA to the load
Size from the calculated demand, then leave room for growth the site can reasonably expect. An undersized unit runs hot and ages its insulation early; a heavily oversized one carries no-load losses for its whole life. For data center and industrial services, account for the harmonic content of drive and UPS loads, which adds heating beyond what the kVA figure alone suggests.
Primary voltage and feed configuration
Confirm the distribution voltage and how the unit sits on the circuit before anything else. Both models cover primaries up to 34.5 kV, which spans the common Texas and Oklahoma distribution classes. Loop feed lets a utility sectionalize an underground loop and restore service from the other direction; radial feed suits a dead-end tap. The single-phase unit is offered in either arrangement.
Dead-front terminations and connectors
Specify the primary bushing interface together with the cable accessories so the pieces match on current rating and voltage class. Dead-front construction keeps energized parts enclosed and connects through separable connectors: a 200A Loadbreak Elbow for hot-stick switching on 15 kV class services, or a 600/900A Deadbreak Elbow where the feeder carries more current.
Efficiency and listings
Check that the unit meets current DOE efficiency rules and any utility or owner listing requirements. Both JST units are UL listed and ANSI/IEEE/CSA/DOE compliant, which covers most utility standards and the documentation EPCs and data center owners ask for at submittal.
For standard ratings and fit, see pad mount transformer sizes, dry type vs liquid for data centers and medium voltage equipment lead times, and match the terminations with our separable connectors.
Frequently asked questions
What sizes do pad mount transformers come in?
Pad mount transformers come in single-phase units for smaller loads and three-phase units for larger ones. JST's single-phase liquid-filled pad mounts run from 15 to 167 kVA, and its three-phase units run from 75 to 5000 kVA, both at primary voltages up to 34.5 kV. Size depends on the connected load, expected growth, motor starting and the utility's standards. Ryan Sales can help match kVA, voltages and loop or radial feed to your project.
Single-phase vs three-phase pad mount?
Single-phase pad mounts serve homes and light commercial loads from one-phase underground laterals, and three-phase pad mounts serve commercial, industrial and multifamily buildings with motors and larger loads. Single-phase units are smaller and often loop-fed along residential circuits. Three-phase units have dead-front compartments with primary and secondary sections. JST makes single-phase pad mounts from 15 to 167 kVA and three-phase units from 75 to 5000 kVA, both built in Wytheville, Virginia.
How long are pad mount transformer lead times?
Pad mount transformer lead times depend on the kVA rating, voltages, special features such as dual voltage or fluid type, the supply of core steel and other materials, and factory backlog. Utility-standard designs and complete specifications move through faster than custom builds. Lead times change often, so Ryan Sales can get current factory lead times for JST single-phase and three-phase pad mount transformers on request.