What we buy
Ranges we buy on this page
This guide covers the arithmetic for raising or lowering voltage by a fixed percentage with a buck-boost transformer.
The calculation separates load kVA from winding kVA. That distinction helps explain why a small buck-boost enclosure can serve a much larger connected load.
| Phase | kVA | Voltage | Fluid |
|---|---|---|---|
| 1-phase | 10 - 333 kVA | up to 25 kV | Liquid or dry |
| 3-phase | 50 - 20,000 kVA | 115 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
A buck-boost transformer has separate windings that are commonly connected in an autotransformer arrangement to add or subtract voltage. Typical winding combinations include 120/240 volts on one side and 12/24 volts on the other.
The terminal diagram determines which combinations are permitted for that unit.
In boost service, the series winding adds its voltage to the incoming supply; in buck service, it subtracts that voltage. This connection does not provide isolation between supply and load.
A 24-volt correction is nominal, because actual winding output follows the voltage applied to the excitation winding.
Local reality
Why it matters when you sell
A nameplate marked 1 kVA does not necessarily mean the installed buck-boost arrangement serves only a 1 kVA load. The series winding handles the correction voltage at load current.
Record the original feeder voltage, output voltage, and connection diagram so the winding rating is not mistaken for system capacity.
For a removed unit from a Greensboro machine bay, a photograph of the terminal links can explain more than an enclosure label alone. Capture the nameplate before cleaning or disconnecting it.
Transformer Buyers NC buys used, surplus, failed, and obsolete transformers throughout North Carolina, including buck-boost units.
Around the site
The numbers
Calculate the required correction as target voltage minus measured supply voltage. Going from 208 to 230 volts requires a 22-volt boost. Divide 22 by 208 and multiply by 100: the increase is about 10.6 percent.
Lowering 240 to 216 volts requires a 24-volt buck, or 10 percent.
For a single-phase load drawing 40 amperes at 230 volts, load capacity is 230 × 40 ÷ 1,000 = 9.2 kVA. The required series-winding capacity is approximately 22 × 40 ÷ 1,000 = 0.88 kVA.
Select the actual unit and connection from the manufacturer’s buck-boost tables, not that calculation alone.
Where it sits
Common mistakes
Do not assume a winding labeled 24 volts delivers exactly 24 volts when its excitation winding receives 208 rather than 240 volts. Ideal proportional output would be 24 × 208 ÷ 240 = 20.8 volts.
Actual output also depends on winding regulation, loading, and the approved terminal connection.
Three-phase sizing cannot be reduced to copying the single-phase example across three enclosures. Load kVA uses square root of three × line voltage × line current ÷ 1,000. Transformer quantity, winding current, neutral requirements, and permissible connections depend on the circuit.
Never create a neutral from an unsuitable buck-boost arrangement.
On the ground
How it affects value
For buyer evaluation, useful capacity depends on both the nameplate winding ratings and the permitted autotransformer connections. A readable 120/240-to-12/24-volt diagram lets an evaluator verify possible corrections.
Missing terminal markings leave uncertainty about polarity and connection options, even when the steel enclosure and mounting feet appear undamaged.
Condition evidence matters alongside the sizing worksheet. Burned terminal insulation, loose links, a scorched winding, or a missing cover changes the assessment of a 1 kVA buck-boost unit.
Include any insulation-resistance report with test voltage and date; that report alone does not establish that damaged windings remain serviceable.
Local reality
What to do next
Before removal, have qualified personnel record supply voltage under representative load, required equipment voltage, phase count, and maximum load current. Keep the machine’s voltage specification with the buck-boost connection sheet.
A fixed-ratio correction follows supply changes; it does not hold a 230-volt output constant as incoming voltage varies.
After isolation, lockout, and verification of absence of voltage, photograph the nameplate, terminals, enclosure, and mounting arrangement. Record dimensions and any handling restrictions at the North Carolina facility.
Preserve terminal links with the unit, and identify disconnected conductors on the drawing rather than leaving an undocumented connection for the next evaluator.
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
Is load kVA the same as winding kVA?
No. In a single-phase autotransformer connection, the series winding handles correction voltage times load current. A 22-volt correction at 40 amperes requires approximately 0.88 kVA of series-winding capacity, while a 230-volt, 40-ampere load uses 9.2 kVA. Manufacturer connection tables govern selection.
Service area
Can buck-boost equipment regulate a fluctuating supply?
A conventional buck-boost transformer applies a fixed-ratio correction rather than active voltage regulation. If the incoming 208-volt supply changes, the output changes too. Measure voltage during representative machine operation and compare the corrected range with the equipment manufacturer’s permitted input range.
Payment
What records help identify a disconnected buck-boost?
Provide a readable nameplate, the manufacturer’s terminal diagram, photographs of installed links, and the former supply and load voltages. Include phase count and load current if known. Label a failed unit’s symptoms specifically, such as burned insulation at a terminal or an open winding.
Logistics
How it affects value: what should a seller know?
For buyer evaluation, useful capacity depends on both the nameplate winding ratings and the permitted autotransformer connections. A readable 120/240-to-12/24-volt diagram lets an evaluator verify possible corrections.