What we buy
Ranges we buy on this page
This guide explains why non-linear loads can overheat transformer windings even when measured current stays below the nameplate rating, and what K-factor measures.
| Phase | kVA | Voltage | Fluid |
|---|---|---|---|
| 1-phase | 10 - 333 kVA | up to 25 kV | Liquid or dry |
| 3-phase | 15 - 20,000 kVA | 34.5 kV | Liquid or dry |
Who we buy from
Six kinds of seller
- Recyclers
- Electrical contractors
- Equipment dealers
- End users
- Demo contractors
- Distributors
Fast offers
A written offer the same business day, based on your photographs.
Dedicated logistics
Our own crew, trailer and crane, not a brokered haul.
No broker fees
One buyer from first call to cleared pad, with nothing skimmed.
How it works
Six steps from photograph to payment
- 01
Take pictures
Photograph the nameplate, the inside of the cabinet and the tank from both ends. Four frames on a phone are enough to price most units.
- 02
Send them to us
Email or text the photographs with the site address and whether the unit is still energised. We reply the same business day with questions or a number.
- 03
Review the offer
The offer names the unit, the site, the price and the pickup window. It is written, dated and good for thirty days unless the unit changes hands.
- 04
We schedule freight
A crew, a trailer and a crane if the pad needs one. You get the date and the arrival window, and the site does not have to close for it.
- 05
Testing on arrival
Winding resistance, insulation resistance and a turns ratio check, plus oil analysis where the unit is liquid-filled. Results travel with the unit.
- 06
Get paid
Payment is released against the signed bill of sale and the scale ticket, by check or ACH, with the paperwork copy left on site.
What we handle
The parts sellers dread
Rigging
Crane, skates and a route survey for anything that will not roll onto a trailer.
Oil containment
Pans, absorbent and a spill plan before a drain plug is touched.
Bill of sale
A document that clears a lien, a lease or a bankruptcy file, not a handwritten note.
PCB paperwork
Testing and manifesting for pre-1979 oil, handled before the unit moves.
On the ground
What it is
Harmonics are voltage or current components at integer multiples of the fundamental frequency. On a 60 Hz system, the third harmonic is 180 Hz and the fifth is 300 Hz.
Rectifiers in variable-frequency drives and UPS equipment draw distorted current rather than a clean sine wave.
That distorted current increases winding eddy-current losses and can add heating in conductors, clamps, and other metal parts. Triplen harmonics, including the third and ninth, can accumulate in a four-wire system's neutral.
A hot neutral termination or discolored winding insulation deserves investigation, not an assumption about ordinary overload.
Local reality
Why it matters when you sell
A transformer removed from a North Carolina hospital UPS room may have carried substantial harmonic current without exceeding its rated amperes. Its operating history helps explain winding discoloration, repeated temperature alarms, or shortened insulation life.
Those details matter when assessing whether the unit is suitable for further service.
Transformer Buyers NC buys used, surplus, failed, and obsolete transformers throughout North Carolina. For equipment connected to drives or rectifier loads, provide temperature logs, maintenance reports, and any power-quality measurements.
Describe whether alarms occurred at steady production, during motor acceleration, or after a UPS or drive-panel expansion was completed.
Around the site
The numbers
K-factor expresses harmonic heating severity by weighting each harmonic current component by the square of its harmonic order, using normalized current values. Higher-order current therefore matters disproportionately.
A K-rated transformer is designed for specified harmonic loading; its marking is not a measurement of the actual connected load at your facility.
Common markings include K-4, K-13, and K-20, but selection requires the load spectrum and applicable design criteria. Record true-RMS phase current, neutral current, current THD, voltage THD, and loading conditions.
A 480Y/277 V nameplate identifies system voltage; it does not establish the transformer's tolerance for harmonic current or resulting heat.
Where it sits
Common mistakes
Comparing only measured amperes with nameplate amperes misses harmonic heating. Two loads with equal RMS current can produce different winding losses because their harmonic spectra differ. An average-responding clamp meter can also misread distorted waveforms.
Use suitable true-RMS instruments and a power-quality analyzer when documenting suspected harmonic overload conditions.
Do not treat a K-13 marking as proof that a transformer removes harmonics from the circuit. Harmonic mitigation depends on equipment design and system configuration.
Likewise, a hot tank or enclosure does not prove harmonics caused the problem; blocked ventilation, loose connections, fan failures, and ordinary overload require investigation.
On the ground
How it affects value
Harmonic history affects the assessment of remaining service suitability, not just the interpretation of a K-factor label. A legible K-rated nameplate helps identify construction, while repeated winding-temperature alarms raise condition questions.
Evidence of cooked insulation, damaged lead connections, or failed temperature sensors can change the appropriate disposition of that unit.
Test records carry more weight than a statement that the transformer ran hot. Insulation-resistance results, turns-ratio tests, winding-resistance measurements, and applicable oil tests help define condition, although no single test rules out thermal aging.
Include dates and test conditions so readings from a cold outage are not confused with operating measurements.
Local reality
What to do next
Before shutdown, have qualified personnel capture the load spectrum under representative operation, if safe access permits. Photograph the nameplate, K-factor marking, temperature controller, neutral terminals, and ventilation openings.
Identify connected UPS modules or drive panels and retain the one-line diagram showing winding connections, grounding, and any harmonic filters already installed.
After isolation, lockout, and verification of absence of voltage, document visible heat damage without opening energized compartments. For a North Carolina removal, record transformer dimensions, lifting provisions, access restrictions, and whether the unit is dry-type or liquid-filled.
Keep harmonic measurements with the inspection file rather than relying on a remembered alarm.
Get started
Get an offer in minutes
Five fields is all it takes. Photographs help, but a nameplate and a town are enough to start.
No fee, no obligation. We reply the same business day.
Tell us what you have
We reply the same business day.
Questions
Straight answers
Equipment types
Can harmonics overheat a transformer below rated current?
Yes. Harmonic current can increase winding eddy-current losses enough to create excessive heating even below nameplate amperes. Assess the harmonic spectrum, actual loading, cooling conditions, and temperature history together. A single true-RMS current reading does not establish acceptable winding temperature.
Service area
Does a K-rated transformer eliminate harmonic currents?
No. A K-rating describes capability to accommodate specified harmonic loading without exceeding design temperature limits under rated conditions. It does not mean the transformer filters harmonic current. Mitigation may require filters, different rectifier arrangements, or other measures based on a power-quality assessment.
Payment
Which harmonic records should accompany a used transformer?
Include the nameplate photograph, K-factor marking, dated harmonic spectrum, phase and neutral currents, and temperature logs. Identify the UPS or drive loads operating during measurement. Maintenance reports describing overheated terminals, winding alarms, or cooling repairs help connect the measurements to equipment condition.
Logistics
How it affects value: what should a seller know?
Harmonic history affects the assessment of remaining service suitability, not just the interpretation of a K-factor label. A legible K-rated nameplate helps identify construction, while repeated winding-temperature alarms raise condition questions.