Attribute Schema Library
Attribute schemaelectrical distribution

Dry-Type Transformers Attributes

A dry-type transformer changes voltage using air and solid insulation instead of oil. The volume in electrical distribution is general-purpose low-voltage units — 480 V delta in, 208Y/120 V out, 15 to 500 kVA — feeding panelboards in commercial buildings, schools, and light industrial plants. Buyers are contractors working off a Division 26 spec, plant electricians replacing a failed unit, and engineers sizing a new service.

The category is a variant explosion. kVA x phase x primary x secondary x rise x enclosure x K-factor multiplies into thousands of near-identical SKUs whose differences live in a catalog-number suffix rather than a field. Acme, Hammond, Eaton, Schneider, and Jefferson each encode those suffixes differently, and all of them ship the real specs as PDF tables — impedance, sound level, taps, and weight sit in a grid on page 7, not in the EDI 832 feed.

Standards drift on top of that. DOE 2016 is still the in-force efficiency level and the amended rule does not bite until April 2029, while thirteen transformer types sit outside the DOE definition entirely.

Core

Every SKU needs these. Without them the record is not a product, it is a row.

kVA Rating
number · kVA
112.5

The rating everything else hangs off. Drives enclosure size, impedance, sound level band, and which DOE efficiency target applies.

Phase
enum
Three-phase

Single-phase and three-phase are not interchangeable. First filter a buyer touches after kVA.

Primary Voltage
enum · V
480 V Delta

Must match the feeder. 480 V delta, 240x480, and 600 V class are distinct SKUs, not configurable options.

Secondary Voltage
enum · V
208Y/120 V

Decides whether the buyer gets a neutral. 208Y/120 feeds receptacle panels; 240 delta does not.

Temperature Rise
enum · °C
150 °C

80/115/150 °C. Lower rise buys overload headroom and lower losses at the same kVA, paid for in copper, weight, and money.

Enclosure / NEMA Rating
enum
NEMA 3R

NEMA 1 indoor, 2 drip-proof, 3R outdoor, 4X corrosive. Wrong rating fails inspection on an outdoor pad.

Construction Class
enum
Ventilated

Ventilated, encapsulated, or TENV. Dust, lint, and corrosive air rule out ventilated; TENV also sits outside DOE scope.

Mounting
enum
Floor

Wall, floor, or trapeze. Wall brackets run out around 75 kVA; above that the buyer needs floor or pad space.

Manufacturer Part Number
identifier
T3112K0013B

The number the counter, the rep, and the buyer all actually use. Suffixes encode shield, taps, and enclosure.

Differentiating

What buyers actually compare on. This is where catalogs win or lose the filter.

Impedance (%Z)
number · %
4.0

Feeds the fault current and AIC study. Typically 3-6.5%; the nameplate value drives downstream breaker selection.

Primary Taps
text
6 @ 2.5% — 2 FCAN, 4 FCBN

Lets the installer correct incoming voltage roughly 5% above and 10% below nominal without changing the unit.

Sound Level
number · dB(A)
50

NEMA ST-20 caps dB(A) by kVA band. Decides whether the unit can sit near classrooms, offices, or patient rooms.

K-Factor Rating
enum
K-13

K-1 to K-40. Nonlinear loads — VFDs, LED drivers, IT gear — overheat neutrals and windings without a K-rated unit.

Electrostatic Shield
boolean
true

Grounded shield between windings attenuates common-mode noise. Routine Division 26 callout, usually hidden in a suffix.

Compliance & identifiers

Standards, regulatory data, and the identifiers channels reject you for missing.

DOE Efficiency Status
enum
DOE 2016 compliant

Records the standard vintage and whether the unit is in DOE scope at all. Thirteen types are excluded by definition.

UL 1561 Listing
enum
UL 1561 Listed

The NRTL mark inspectors look for on general-purpose dry-type units. No listing, no sign-off.

GTIN / UPC
identifier
047503092422

Required by the IDW, by marketplaces, and by every barcode scan in the warehouse.

Country of Origin
identifier
Mexico

Drives duty, TAA eligibility, and federal procurement. Frequently differs by kVA within one brand's line.

The fields that aren't in the schema at all

What most dry-type transformers catalogs are missing.

The table above is the schema most catalogs already have. These are the attributes that usually aren't in it — each one surfaced by a signal from the live market rather than by an audit of what's already there. This is what Anglera's Schema Foundry does on a real catalog, in this category.

Supplier signal
+ Impedance (%Z)

Engineers ask for %Z on nearly every RFQ because the fault current study needs it. It lives in a datasheet grid keyed by kVA and voltage; almost no distributor catalog exposes it as a field.

Buyer can't finish the AIC calculation from the product page, so they RFQ. The quote goes to whoever answers first and the catalog loses a sale it had already won.

Competitor signal
+ DOE Efficiency Status (scope + vintage)

Rexel and Platt carry 'DOE 2016' inside the product title string, not as a facet. Thirteen types — TENV and drive isolation among them — sit outside the DOE definition, and nothing records which.

A DOE filter built from title text silently drops legitimately exempt TENV and drive-isolation stock out of results, and buyers conclude you don't carry it.

Search signal
+ BABA / Domestic Content Status

Buyers search 'BABA compliant transformer' and land on a manufacturer PDF letter, not a product. Distributor catalogs carry no domestic-content field, so the federally funded segment is unfilterable.

Federally funded projects can't be quoted from the site. The order routes to a manufacturer rep who can produce the letter, and the distributor never sees the RFQ.

Review signal
+ Sound Level (dB(A))

Complaints about hum in occupied spaces show up post-install. NEMA ST-20 caps dB(A) by kVA band and manufacturers publish the tested figure, but catalogs carry no field to filter on.

Units get specced out of noise-sensitive installs, or get installed and pulled. That surfaces as a return or a change order, never as a lost filter.

Supplier signal
+ Primary Taps

Tap configuration is one line in the manufacturer's PDF table — '6 @ 2.5%, 2 FCAN, 4 FCBN' — and disappears in transfer to the catalog. Encapsulated units often have none, also unrecorded.

Contractor discovers on site that incoming voltage runs high and the unit has no taps to correct it. That's a truck roll and a restock, not a filter miss.

How Schema Foundry finds these

Messy in, governed out.

The same value, spelled every way electrical distribution suppliers spell it. A filter only works once they agree.

kVA Rating
112.5112.50112.5 KVA112500 VA112,5 kVA112.5KVA
112.5 kVA

112.5 vs 112.50 splits one product into two facet buckets; a VA-denominated value sinks to the bottom of any numeric sort.

Secondary Voltage
208Y/120208/120120/208V208 Wye208Y/120 Volts208V 3PH 4W
208Y/120 V

208Y/120 (four-wire, neutral) and 208 V delta (three-wire) are different products. Collapsing them ships a unit with no neutral.

Temperature Rise
150C150°C RiseRise: 150 C150 Deg CTEMP RISE 150CClass 150
150 °C

Rise is a three-value enum (80/115/150). Free-text spellings make it unfilterable, so buyers fall back to reading PDFs.

Enclosure / NEMA Rating
NEMA 3R3RType 3RN3RNEMA-3ROutdoor
NEMA 3R

'Outdoor' is not a rating. Inspectors cite the Type number, and NEMA 2 plus a weathershield kit is not the same SKU as native 3R.

What buyers ask

Every one of these should be answerable from the attributes above. If it isn't, that's a gap.

  • What's the %Z? I need it for the fault current study before I can size the breaker.
  • Is this DOE 2016 compliant, or is it one of the exempt types?
  • Can I wall-mount 112.5 kVA or does it have to sit on the floor?
  • Is it native NEMA 3R, or NEMA 2 that needs a weathershield kit added?
  • Does it have primary taps? My incoming voltage runs about 5% high.
  • How loud is it? It's going in a closet next to an occupied office.
  • Will the 208Y/120 secondary give me a neutral for the receptacle panel?
  • Is it BABA compliant? The job is federally funded.

What channels require

The same SKU, different mandatory fields per destination.

IDEA Industry Data Warehouse (IDW)
Manufacturer Part NumberGTIN / UPCUNSPSC codeElectrical Attribute Schema valuesCountry of OriginSpec sheet URL
Distributor filter rail (Graybar, Rexel, Platt)
kVA RatingPhasePrimary VoltageSecondary VoltageEnclosure / NEMA RatingTemperature Rise
Amazon Business
GTIN / UPCBrandManufacturer Part NumberShipping weightProduct dimensionsCountry of Origin
Federal / BABA-funded RFQ
Country of OriginBABA / Domestic Content StatusUNSPSC codeManufacturer Part NumberDOE Efficiency Status

Dry-Type Transformers data, in practice

Which dry-type transformers are exempt from the DOE efficiency standard?

10 CFR 431 Subpart K defines a distribution transformer as 34.5 kV or less in, 600 V or less out, 60 Hz, 15-2500 kVA dry-type. It then excludes thirteen types: autotransformer, drive (isolation), grounding, machine-tool (control), nonventilated, rectifier, regulating, sealed, special-impedance, testing, tap range of 20% or more, UPS, and welding. The trap: TENV units are nonventilated and therefore out of scope, so a 'DOE 2016' filter built from title text hides legitimate stock. K-factor units are not exempt — NEMA TP-1 1996 excluded high-harmonic transformers, but DOE has covered them since 2007. Model the field as scope plus vintage, not a boolean badge.

Does the 2024 DOE rule change what I stock today?

Not yet. The amended standards published April 22, 2024 carry a compliance date of April 23, 2029. Units built before then follow the 2016 levels, which are measured at 35% of nameplate load, temperature-corrected to 75 °C. The final rule also stepped back from the 2023 proposal's near-total amorphous core requirement, allowing roughly 75% of cores to remain grain-oriented electrical steel. What it means for data: 'DOE 2016' is a dated claim. Carry the standard vintage as a governed value rather than baking it into description text, or you will be re-editing every SKU in the category in 2029.

Why does temperature rise matter if two units are both 150 kVA?

Rise is the average winding temperature above ambient. An 80 °C rise unit inside a 220 °C insulation system has far more thermal headroom than a 150 °C rise unit in the same system, so it tolerates overload and runs cooler at the same nameplate. It is also larger, heavier, and more expensive, because you buy headroom with copper and steel. Buyers who spec 80 °C or 115 °C rise are usually protecting against future load growth or harmonic heating. Treat rise as a governed three-value enum (80/115/150 °C) and keep insulation system class as its own field — they are related but not the same thing, and suppliers conflate them.

What is an electrostatic shield, and should it be a filter?

A grounded copper or aluminum shield between primary and secondary windings that attenuates common-mode line noise and transients before they reach the secondary. It is a routine Division 26 callout for units feeding data centers, medical imaging, lab instruments, and PLC panels. Manufacturers typically encode it in the catalog-number suffix rather than a field — Hammond's 'S' suffix, for example — so it stays invisible to search. If a buyer can't filter for it, they RFQ it, and the RFQ goes to whoever answers fastest. It is a cheap field to carry and a common reason a shielded unit loses to an identical one that was findable.

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