What we buy
Ranges we buy on this page
This guide explains why a transformer can draw several times its rated current during energization, even with the secondary breaker open. It covers core saturation, residual magnetism, switching conditions, and the effect on fuses and protective relays.
| 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
The short version
Inrush is a temporary magnetizing current, not the current demanded by the connected load. When a breaker closes, the applied voltage can drive the core into saturation.
The winding then draws a sharply peaked, asymmetric current that may operate protection before the transformer settles into normal service.
The first current peaks can reach several times rated current, but there is no universal multiplier or duration. Residual flux, the point on the voltage wave at closing, core construction, and source impedance all matter.
A 480-volt secondary can remain unloaded while substantial primary inrush flows.
Local reality
Why a seller should care
An energization trip does not, by itself, establish that a winding has failed. For an owner retiring a North Carolina plant transformer, the distinction matters to equipment assessment.
A relay event report showing transient magnetizing current tells a different story from sustained differential current or a failed insulation test.
Keep the nameplate photograph, one-line diagram, relay settings, and switching log with the transformer record. Note whether the trip occurred on first energization, after an outage, or during feeder restoration.
Those details help separate an inrush-related protection operation from a bushing flashover, cable fault, or internal winding problem.
Around the site
The arithmetic
For a three-phase transformer, rated line current equals kVA multiplied by 1,000, divided by the square root of three times line-to-line volts.
A 1,000-kVA unit rated 13,200 volts primary and 480 volts secondary has rated currents of approximately 43.7 amperes primary and 1,203 amperes secondary.
If a measured primary peak reaches eight times 43.7 amperes, that is about 350 amperes instantaneous, not necessarily 350 amperes RMS. Do not compare that peak directly with a fuse curve or relay pickup without checking the measurement basis.
Protection analysis needs the waveform, duration, and device response.
Where it sits
Where people go wrong
Raising an instantaneous pickup until the breaker stops tripping can hide a protection coordination problem. The revised setting must still detect faults and coordinate with upstream and downstream devices.
Use the actual transformer data, available fault current, fuse curves, and relay logic rather than a generic inrush multiplier.
Another mistake is treating second-harmonic content as an absolute verdict. Many differential relays use harmonic restraint or blocking to recognize inrush, but algorithms and thresholds differ.
Review the specific relay manual and event oscillography; low second-harmonic content alone does not prove an internal fault, or exclude magnetizing inrush.
On the ground
Value impact
For a used transformer assessment, a documented inrush trip is more informative than a tag reading bad transformer. We buy used, surplus, failed, and obsolete transformers across North Carolina.
Records showing the trip timing, protection response, and subsequent testing help describe the unit accurately without assuming it is serviceable.
Burned bushings, a distorted tank, abnormal dissolved gas results, or evidence of winding movement require separate evaluation; inrush is not an explanation for every defect. Preserve test reports and photographs before disconnecting cables or removing radiators.
Missing records leave uncertainty about whether the trip was transient or fault-related.
Local reality
Your next move
Before another energization attempt, have qualified personnel review the switching sequence and protection records under the site's electrical safety procedures. Do not repeatedly close a breaker into an unexplained trip.
Check cable connections, insulation test results, grounding, and relay targets before deciding whether further diagnostic testing is appropriate.
If removal is already planned, assemble the nameplate data, dimensions, estimated weight, fluid information, and energization history. Identify whether the transformer remains on its pad or has been disconnected and staged.
Transformer Buyers NC uses those records to assess the equipment and plan access for lifting and pickup.
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 inrush occur with the secondary breaker open?
Yes. Magnetizing inrush flows when the primary winding establishes flux in the core, even without secondary load. An open 480-volt secondary breaker does not prevent it. The primary protection can therefore operate during energization while no load current leaves the secondary terminals.
Service area
Does an energization trip mean the transformer failed?
No. Inrush can operate a fuse or relay without an internal transformer fault, but the trip still needs investigation. Compare relay targets and waveform records with insulation tests, bushing condition, and the switching log. Do not classify the unit from the breaker position alone.
Payment
Which records help distinguish inrush from a fault?
Keep relay oscillography, sequence-of-events records, protection settings, and the exact breaker closing time. Include the one-line diagram and transformer nameplate. Current asymmetry, harmonic content, decay, and relay operation provide useful clues, but interpretation must account for the relay design and any current transformer saturation.
Logistics
Value impact: what should a seller know?
For a used transformer assessment, a documented inrush trip is more informative than a tag reading bad transformer. We buy used, surplus, failed, and obsolete transformers across North Carolina.