MGM Transformer K-Factor rated dry-type transformers (K-4 / K-9 / K-13)

MGM K-Factor dry-type transformers, 15 to 1,000 kVA harmonic-rated units from a stocked California line

MGM Transformer K-Factor rated dry-type transformers (K-4 / K-9 / K-13) is one of 32 data center transformers tracked in the SecondWatt catalogue, each with specifications, lead times and indicative secondary-market pricing.

MGM Transformer K-Factor dossier: K-4 to K-13 dry-types, 15-1,000 kVA, DOE 2016 compliance, harmonic-load guidance, inspection checklist, failures.

MGM Transformer Company of Commerce, California builds low- and medium-voltage dry-type (VPI and cast coil) and liquid-filled lines, and its K-Factor series addresses non-linear loads. Catalog coverage confirms K-4, K-9, and K-13 ratings at 15-1,000 kVA with 480 and 600 V delta primaries into 208Y/120 and 480Y/277 secondaries at 150 C rise, DOE 2016 compliant under 10 CFR 431, UL and CSA listed, designed and tested to NEMA, ANSI, and IEEE practice. A K-20 tier does not appear in the catalog. K-factor matters because harmonic-rich loads (UPS front ends, VFDs, LED and server power supplies) drive eddy losses that overheat standard transformers; a K-13 unit carries the same nameplate kVA at full non-linear duty. MGM backs the line with a stocked general-purpose program that ships fast from California inventory, a 2025 Inc. 5000 listing signaling growth. Secondary supply is thin and mostly unpriced: a used 75 kVA MGM dry-type sat live at a dealer without a published price, and the LV dry class generally trades price-on-request outside commodity general-purpose sizes.

Why it matters

Every modern data hall load is non-linear, and under-K-rated transformers fail early from harmonic heating, a failure mode invisible until thermal scans catch it. K-rated supply protects nameplate capacity at real duty. MGM is one of the few independents publishing a full K-Factor catalog with DOE 2016 compliance, making it the reference spec for the class.

Who buys it

Electrical contractors and engineers serving data centers, broadcast, medical imaging, and industrial automation specify K-rated units wherever measured load profiles show harmonic content. West Coast buyers value MGM's stocked program against 20-32 week class leads; used buyers accept unpriced dealer stock because testing costs stay small at this scale.

Role in the data center

K-13 step-down units feeding PDU and mechanical loads with harmonic-rich profiles, holding nameplate capacity where standard units derate.

Key specifications

Technical summary

K-factor tiers: K-4, K-9, K-13 (no K-20 in catalog) Range: 15-1,000 kVA Primaries: 480 delta, 600 delta Secondaries: 208Y/120, 480Y/277 Temperature rise: 150 C standard Efficiency: DOE 2016 per 10 CFR 431 Listings: UL, CSA Design/test: NEMA, ANSI, IEEE practice Stocked program: general-purpose LV dry, fast ship from California Company: Commerce CA; 2025 Inc. 5000 honoree Companion lines: VPI and cast coil MV dry-type, liquid pad-mount

Pricing and availability

Comparable secondary-market band: 2595–9495 $ per unit. Trend: up Lead time, new: Stocked sizes fast-ship; 20-32 weeks class otherwise. Lead time, used or refurbished: 1-4 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.

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

MGM distribution and the stocked program for new; Genemco and general surplus dealers for used (observed 75 kVA unit unpriced); eBay and Electrical Trader for the wider LV dry class.