Markets & Applications

EV chargers are power-electronics loads, not resistive loads — so the transformer that feeds them must be sized for coincidence, harmonic heating and fault current, not just connected kVA. This guide gives the three-step sizing method, the K-factor and IEEE C57.110 derating rules, and the specification points that keep a charging hub from overheating its transformer.

A solar step-up transformer is sized on the plant's real inverter AC output — not the array's peak DC rating — and must survive harmonic-rich, part-load, outdoor duty. This guide gives the three-step sizing method, the voltage architectures from 0.4/0.8 kV to 35 kV, the K-factor and IEEE C57.110 derating rules, and the specification points that keep a PV plant from tripping at solar noon.

A wind farm steps power up in two stages: a turbine (WTG) transformer sized on generator apparent power and harmonic duty, then a farm substation transformer sized on total coincident output. This guide gives the three-step sizing method for both, the 0.69 kV → 33 kV → 110/220 kV voltage architecture, the K-factor and IEEE C57.110 derating rules that converter turbines demand, and the onshore-versus-offshore specification differences that decide whether the unit lasts 20 years.

A battery storage plant steps voltage up in one or two stages: a PCS unit transformer sized on converter apparent power and harmonic duty, then a grid transformer sized on coincident plant output. This guide gives the four-step sizing method, the 0.4/0.69 kV → 33 kV → 110/220 kV architecture, the K-factor and IEEE C57.110 derating rules PWM converters demand, the cyclic-duty loss economics that decide the loss grade, and the tap-changer, cooling and fire-safety choices grid-forming storage forces.

Data center transformers are sized on after-diversity design load, then multiplied by redundancy (N+1, 2N). Learn how AI rack density, IT harmonics and loss grade set the specification.

Green hydrogen plants need a purpose-built rectifier (converter) transformer, sized on stack DC power and specified for harmonic-rich, high-current duty. Learn the six-step sizing method, 6/12/24-pulse selection against IEEE 519, K-factor derating, impedance and tap choices, hazardous-area rules and the datasheet checklist.

Shore power (cold ironing) needs a purpose-built port transformer: the medium-voltage grid stepped down to the 6.6 kV or 11 kV shore connection, sized on the ship's berth load and specified for harmonic-rich reefer and converter loads, salt-air corrosion and long cable runs. Learn the six-step sizing method, the 50 Hz / 60 Hz trap (a transformer changes voltage, not frequency), IEC/IEEE 80005-1 shore-side requirements and the full datasheet checklist.

A railway traction transformer is specified by the traction system, not by kVA: 25 kV 50/60 Hz, 15 kV 16.7 Hz or DC rectifier duty each change the core, insulation and connection. Learn the six-step sizing method, how V/v and Scott connections control negative-sequence unbalance, why 2x25 kV autotransformer feeding changes the design, and what IEC 62695 / EN 50329 and IEC 61378-1 require in the specification and tests.

A mine site transformer is sized from the mine's load cycle, not from a kVA table: crushers, mills, conveyors and shovels are shock and harmonic loads, and the cable that reaches them often sets the limit before the transformer does. Learn the six-step sizing method, how VFD harmonics drive K-factor and derating, why pit feeders are built at 6.6/11/33 kV, and what enclosure, IP rating, protection and tests a quarry or underground mine substation requires.

A desalination plant transformer is sized from the RO train's pump duty and a harmonic study, not from a kVA-per-m3 rule: high-pressure pumps dominate the load, VFD rectifiers set the harmonic and K-factor duty, big motors set the starting voltage dip, and a coastal site sets the corrosion class. Learn the six-step SWRO sizing method, the 33/11 kV architecture, converter-transformer specification to IEC 61378-1, IEEE C57.110 derating, N-1 redundancy and coastal enclosure requirements.

An electric arc furnace transformer is sized from the melt shop's energy and power profile, not from a kVA-per-tonne table: melting energy divided by power-on time sets the average arc power, the meltdown peak and the arc-circuit power factor set the MVA, and the secondary current in kA sets the low-voltage winding, bushings, water-cooled busbars and cooling. This guide gives the six-step sizing method with a worked 100-tonne example, the 840-480 V tap range and constant-current tap behaviour, why the secondary is delta-connected, the impedance and series-reactor rules for arc stability, harmonic derating and IEC 61000-3-7 flicker limits (Pst 1.0 / Plt 0.8), short-circuit and inrush duty, cooling in a hot melt shop, protection, and an RFQ parameter table for buyers.

A cement plant transformer is sized from the grinding and pyro-process load list and from mill starting duty, not from a kVA-per-tonne table: specific electrical consumption of roughly 90-110 kWh per tonne of cement is converted into an area-by-area load list, demand and diversity factors give the running kVA, and then the motor-starting voltage dip, the harmonic duty of the mill and fan drives, and the hot, dusty kiln-side environment move that figure by a rating step or more. This guide gives the six-step method with a worked example, the mill starting-method trade (DOL, slip-ring, soft starter, VFD), harmonic and K-factor specification, enclosure, IP class and creepage for cement dust, dry-type versus oil-immersed selection by location, grid versus captive power and waste-heat recovery, a full RFQ parameter table, the tests that prove the unit, cost drivers, 25-year maintenance planning around the annual kiln shutdown, and five specification mistakes that cost cement projects money.

A refinery transformer is sized from the process load list and from the consequence of losing a unit, not from kVA per barrel. This guide covers the 132/33/11 kV architecture, hazardous area classification under IEC 60079 and NEC Article 500, motor starting of 5-16 MW compressors, VFD harmonic derating, impedance and arc flash trade-offs, 2x100% redundancy, C5-M corrosion, and 20-year loss capitalisation.

A paper mill transformer is sized from the area load list and from the ride-through requirement of the paper machine, not from kWh per tonne. This guide covers the 132/33/11 kV architecture, the 690 V sectional drive bus, IEEE C57.110 harmonic derating for 6-pulse and AFE drives, the 12 MW refiner start that sets the bus strength, refiner starting methods compared by voltage dip, impedance selection against fault level, dry-type versus oil by mill location, C5-M corrosion in the bleach plant, mill generation and reverse power, and loss capitalisation at 8,000 hours a year.

An airport transformer is sized from an area load list with airport-specific diversity, not from a watts-per-square-metre benchmark. This guide covers the terminal load list and demand factors behind an 11-12 MVA substation, the 400 Hz ground power transformer that is part of a 90-180 kVA converter, the 6.6 A series runway lighting circuit with one isolation transformer per lamp, N+1 firm capacity, K-factor and IEEE C57.110 derating for baggage drives and constant current regulators, impedance selection against 30-48 kA LV fault levels, generator sizing for transformer inrush, C5-M coastal corrosion, and the datasheet fields that make two airport offers comparable.

A container terminal transformer is sized from a crane fleet load list with duty-cycle demand factors, not from installed kVA. This guide covers STS and RMG crane demand factors (0.40-0.50 on installed kVA), the 10-minute RMS and hot-spot method behind a 1,600 kVA crane transformer, reefer plug demand (5-9 kW per 40-ft unit, 22 kVA plug rating, 0.65 diversity), the worked 23 MVA terminal substation calculation, 6-pulse versus 12-pulse versus AFE harmonics and K-factor derating per IEEE C57.110, the 400 V versus 6.6/11 kV voltage-drop comparison that decides the quay voltage, regenerative braking and reverse power, dry-type versus oil-immersed by location, IP55 and ISO 12944 C5-M corrosion requirements, N-1 sectionalised crane buses, impedance and voltage dip, and the datasheet fields that make two terminal offers comparable.

A hydro GSU is sized from generator MVA, not turbine MW: 60 MW at 0.90 pf needs 75 MVA. This guide covers the five-step sizing calculation, impedance and tap-range selection for remote weak grids, load-rejection over-flux limits (1.10/1.25/1.40 pu), start-stop thermal cycling per IEC 60076-7, cooling stages from ONAN to ODWF, altitude derating, the factory test list including short-circuit, PD and FRA, and indicative FOB cost ranges by voltage class.

A district heating transformer is sized by its pumps, not its MW: a 10 MW heat substation needs only 160-250 kVA, while a 25-50 MW CHP generator needs a 40-75 MVA step-up unit. This guide covers the five-step hydraulic-to-electrical sizing calculation, the summer-minimum no-load loss trap, temperature difference as the lever that cuts pumping energy, dry-type versus oil for basement substations, ventilation and noise limits, CHP power-to-heat ratios and tap ranges, heat pump and VFD harmonic duty, and indicative 2026 FOB prices.

A geothermal GSU is sized on generator MVA (1.05–1.10×, 8–12% impedance at 33 kV), not plant MW, while the house load decides the auxiliary transformer: 8–18% of gross for flash plants and 15–30% for air-cooled binary ORC. This guide covers sizing, H2S corrosion specification, 45–50 °C derating, altitude, seismic and load rejection, plus indicative 2026 price bands and loss capitalisation at 8,000 operating hours a year.

A waste-to-energy plant needs a GSU at 1.05–1.10× generator MVA, an auxiliary transformer at 12–22% of gross output and a station transformer for start-up — sized from generator MVA, never from tonnes per day. This guide covers HCl and ammonia-slip corrosion (ISO 12944 C5/CX), 45–55 °C derating, K-factor selection for VFD fans and ACCs, grid-code protection, test scope, and indicative 2026 price bands with loss capitalisation at 7,500 operating hours a year.

A biomass plant needs a GSU at 1.05–1.10× generator MVA, a unit auxiliary transformer at 10–17% of gross output and a station transformer for start-up — sized from generator MVA, never from boiler tonnes per hour. This guide covers weak rural grid compliance (SCR 3–8, 0.95 leading pf, tap range), fuel-yard dust and fire protection (IP54/IP55, ISO 12944 C4/C5), IEEE C57.110 harmonic derating for VFD loads, 45–50 °C derating, noise limits near villages, test scope and indicative 2026 FOB price bands with loss capitalisation at 6,500 operating hours a year.

A wafer fab needs utility service transformers of 60-100 MVA at 230/34.5 kV, MV/LV unit substations of 2.0-2.5 MVA at 13.8/0.48 kV and small tool-level isolation units, sized from connected tool load at a 0.55-0.70 demand factor, never from nameplate summation. This guide covers the five transformer duties, SEMI F47 sag ride-through and static transfer switching, 2N redundancy and arc-flash limits, cast-resin versus oil-immersed selection, IEEE C57.110 harmonic derating at 25-30% THD, cleanroom noise and seismic constraints, loss capitalisation at 8,760 operating hours, test scope and indicative 2026 FOB price bands.

Size a wastewater plant transformer from connected load × 0.62: 2×2,500 kVA, K-13 harmonic derating, IP54 cast resin, NFPA 820 zoning and 20-year loss evaluation.

Size a car plant transformer from connected load x 0.50: 42,580 kW becomes 21,330 kW, 23,236 kVA, 2x25 MVA 33/11 kV mains, K-4 body-shop units and 690 V for the press line.

A 288-pot, 420 kA potline is 514 MW DC at 1,224 V: six 87 MVA rectiformers at 70 kA, 8.5% impedance held to ±2.5%, 165 MVAr of filtering and 2 x 400 MVA mains run to a current-reduction protocol.

A 20,000 TCD mill is 33.5 MW of load on 100 MW of cogen: 2 x 50 MVA 138 kV GSUs at 96% N-1, 8% mill-transformer impedance to hold shredder starts to a 7% dip, and 12-pulse drives to keep TDD under 5%.