Eaton DS-3 / DT-3 ventilated dry-type
Manufacturer: Eaton
Eaton DS-3 and DT-3 ventilated dry-type transformers, the 600 V class workhorses of low-voltage distribution.
This model is part of SecondWatt’s transformer research catalogue. Specifications and price observations are included where supported by sources. Equipment availability and commercial terms require confirmation.
Eaton DS-3/DT-3 dry-type dossier: 7.5-1,500 kVA at 600 V class, DOE 2016 efficiency, used units from 1,500 USD, inspection checklist, failure points.
Eaton's low-voltage dry-type lines are the Type DS-3 single-phase and DT-3 three-phase ventilated general purpose transformers, carrying legacy Cutler-Hammer V-prefix catalog numbers. This dossier covers the DS-3 and DT-3 lines. The DS-3/DT-3 range runs 7.5-333 kVA single-phase and 7.5-1,500 kVA three-phase in the 600 V class, with 150 C temperature rise standard and 115 C or 80 C options, NEMA 2 enclosures (3R with weathershields), aluminum or copper windings, and DOE 2016 efficiency compliance under 10 CFR 431. Low-sound builds run 3-5 dB below NEMA ST-20 limits. The secondary market is active at small dollar figures: a refurbished 75 kVA DT-3 unit (480 to 208Y/120) sold at 1,500 USD with a 1-year warranty in Minnesota, and surplus dealer collections list Eaton alongside Square D, GE, and Federal Pacific dry-types with a site ceiling near 11,499 USD. Distributor stock keeps new-unit availability measured in days.
Why it matters
Every data hall runs on this class: the last transformation before the panelboard. DOE 2016 efficiency rules, amended in 2024 with 2029 compliance, split the fleet into compliant and legacy stock, and Section 232 tariffs of 50% on imported dry-type content from 2025-08-18 push buyers toward domestic and used supply.
Who buys it
Electrical contractors, plant engineers, and data center fit-out teams buy DT-3 class units for 480-to-208Y/120 step-down in electrical rooms, alongside commercial building retrofits. Buyers pick used units for same-day availability at a fraction of distributor price, accepting shorter warranties; the class is a commodity where testing costs can exceed the hardware discount.
Role in the data center
480 V to 208Y/120 step-down for mechanical loads, offices, and low-density IT space; the commodity transformer of every electrical room build-out.
Key specifications
| Single-phase range | 7.5-333 kVA |
|---|---|
| Three-phase range | 7.5-1500 kVA |
| Voltage class | 600 V |
| Temperature rise | 150 std; 115 / 80 optional C |
| Enclosure | NEMA 2; 3R with weathershields |
| Efficiency standard | DOE 2016 (10 CFR 431) |
| Sound option | 3-5 dB below NEMA ST-20 |
| Example distributor SKU | V48M28B7516CU (75 kVA, 480D-208Y/120) |
| Observed refurb price | 1,500 (75 kVA, 1-yr warranty) USD |
Technical summary
Single-phase (DS-3): 7.5-333 kVA Three-phase (DT-3): 7.5-1,500 kVA Voltage class: 600 V Temperature rise: 150 C standard; 115 C / 80 C options Enclosures: NEMA 2 (3R with weathershields) Windings: aluminum or copper Efficiency: DOE 2016 per 10 CFR 431 Sound: low-sound options 3-5 dB below NEMA ST-20 Grounding: NEC 450.10(A) ground bar Legacy catalog lineage: Cutler-Hammer V-prefix numbers MV extension: ventilated MV dry-type line above 600 V
Major variations
DS-3 single-phase versus DT-3 three-phase, aluminum versus copper windings, and rise class (150/115/80 C) are the main axes; MV ventilated dry-type extends the family above 600 V. Power Xpert is a separate Eaton metering product family, not a transformer line.
Configurations and options
The line is Type DS-3 single-phase at 7.5-333 kVA and Type DT-3 three-phase at 7.5-1,500 kVA, in the 600 V class, and the options that move price are winding material, temperature rise, enclosure, sound and efficiency tier. Windings are aluminum or copper. Rise is 150 deg C standard with 115 deg C and 80 deg C options that buy headroom. Enclosures are NEMA 2 standard and NEMA 3R with field-installed weathershields. Low-sound builds run 3 dB or 5 dB below the NEMA ST-20 limit. Eaton lists both DOE 2016 and NEMA TP-1 efficiency variants, and 60 or 50 Hz builds. A used buyer reads the legacy Cutler-Hammer V-prefix catalog number, then kVA, voltages, rise, winding material, enclosure and the efficiency stamp. Tap arrangement, electrostatic shield and K-factor are not listed on the ventilated general purpose page as of September 2026; K-factor units are a separate Eaton line.
Compatibility and dependencies
The unit sits between a 480 V switchboard or panel and 208Y/120 panelboards, typically delta primary to wye secondary, which makes the secondary a separately derived system; Eaton ships the grounding provision that NEC 450.10(A) calls for, and the system bonding jumper and grounding electrode conductor are the installer's work. The 600 V class is a hard ceiling: a medium-voltage feed needs Eaton's ventilated medium-voltage dry-type line instead. Ventilated construction sets the siting constraint, since the enclosure needs clearance for airflow and the room has to remove the losses; NEMA 2 is indoor and NEMA 3R requires the field-installed weathershields. Where the unit sits near occupied space, the low-sound option against the NEMA ST-20 limit is the specification that matters. Harmonic-rich load belongs on the separate K-factor line rather than on a derated general purpose unit.
Pricing and availability
Comparable secondary-market band: 2295–24995 $ per unit. Trend: up Electrical Trader's price history, published 2026-04-01, puts power transformer prices up 77% between 2019 and 2026 with a 45-95% spread by model, and attributes about half the move to materials: copper up roughly 70% and grain-oriented electrical steel up 80-100% between 2020 and 2025, together 50-55% of production cost. The same series shows the annual rate easing, from 34.58% in 2022 to 8-10% in 2025 with 3-5% forecast for 2026. Terrapin Construction Group put dry-type lead times at 0-2 MVA at 20-32 weeks on 2026-06-10. Lead time, new: Distributor stock to 20-32 weeks by size. Lead time, used or refurbished: 1-2 weeks (dealer stock). Warranty, used: 3-year typical from major US rebuilders.
Lifecycle and maintenance
Cast-resin and VPI dry-type transformers typically serve 25-30+ years with minimal maintenance: periodic cleaning, PD testing on critical units, fan service on AF designs, and torque checks. There is no oil system to sample, so temperature and PD are the condition indicators. Rebuild options are limited compared with liquid units; failed coils are usually replaced rather than repaired, which makes pre-purchase PD and visual inspection decisive for used units.
Thermal and emissions profile
Transformers produce no combustion emissions; the regulatory profile is efficiency and fire class. US low-voltage dry-type units fall under DOE 10 CFR 431 efficiency rules (DOE 2016 levels, amended 2024 with 2029 compliance), and EU-market cast-resin units fall under Ecodesign Regulation 548/2014 Tier 2. Dry-type construction removes oil fire and spill risk entirely, which is why cast-resin units carry IEC 60076-11 fire class F1 and serve indoor and environmentally sensitive sites.
Common failure points
- Partial discharge — PD in resin voids degrading insulation toward failure
- Resin cracking — Cracks from thermal cycling or mechanical shock
- Contamination — Dust and conductive debris enabling surface tracking
- Cooling fans — Failed AF fans derating capacity
- Connections — Loose terminations overheating under load
- Overheating under harmonics — Excess temperature on non-linear loads beyond K-rating
Inspection checklist
Partial discharge — PD test per IEC 60270 practice; readings above 10 pC warrant investigation on cast-resin coils Resin condition — inspect all coils per IEC 60076-11 practice for cracks and crazing from thermal cycling; any through-crack fails Insulation resistance — megger HV/LV/ground; polarization index of 2.0 or higher passes Turns ratio — TTR on all tap positions; deviation beyond 0.5% from nameplate fails Winding resistance — three-phase balance within 2% between phases Contamination — inspect for dust and conductive debris between coils; contamination is a leading dry-type failure driver Cooling fans (AF units) — run-test all fans and verify temperature controller setpoints Temperature sensors — verify RTD or thermocouple channels read within 5 C of a reference at ambient Connections — torque-check HV and LV terminations; thermal-scan at first energization and re-check within 12 months Clearances — verify electrical clearances and enclosure IP rating match the installation environment Class verification — confirm fire/environmental/climatic classes (F1, E2/E3, C2/C3) against nameplate Harmonic suitability — verify K-factor rating (K-4/K-13) against the intended non-linear load profile Core and frame — inspect for shipping damage and loose core bolts; verify single core ground Energization test — verify secondary voltage within 5% on all phases and no abnormal sound level Records — factory test certificate, PD test data, and service history; missing PD data reprices the unit
Procurement channels
Distributor stock (State Electric and peers) for new; EMSCO, Electrical Trader, Maddox webstore, and eBay for used and refurbished. The class trades openly with published prices, unusual in the transformer market.
Regional notes
This is a North American 600 V-class product carrying DOE 2016 efficiency compliance under 10 CFR 431, with Eaton also listing NEMA TP-1 and other efficiency variants and both 60 and 50 Hz builds. The compliance date matters on resale: the DOE amended the distribution transformer standards in a final rule published 2024-04-22 with a 2029 compliance date, so a used unit built to TP-1 or to the pre-2016 rules can be reused but may not satisfy a new-project specification. Dry-type transformers fall inside the Section 232 50% tariff on non-US steel and aluminum content applied to derivative products from 2025-08-18.