# Transformers and power electronics: Engineering methods

Transformers, rectifiers, inverters, converters and chargers compared

Source page: https://www.materialinsights.org/energy/e_power_electronics/methods/

What this tab covers The engineering methods that can do this conversion, compared on efficiency, scale, economics, limitations and reliability.

Five families do most of the work: transformers, rectifiers, inverters, DC-DC converters and battery chargers.

#### Comparison

| Method | Efficiency | Scale | Economics | Limitations | Reliability |
|---|---|---|---|---|---|
| **Power and distribution transformers**^[3](https://www.energy.gov/sites/prod/files/Large Power Transformer Study - June 2012_0.pdf)^[4](https://library.e.abb.com/public/929bc703922d49069e6920d5ce6ab9c1/53-57%202m522_EN_72dpi.pdf)^[1](https://www.iea.org/reports/building-the-future-transmission-grid/executive-summary)^[13](https://www.energy.gov/sites/default/files/2024-10/EXEC-2022-001242%20-%20Large%20Power%20Transformer%20Resilience%20Report%207-10-24.pdf) | Typically above 99% | Kilovolt-amperes (distribution) to hundreds of MVA (power) | Large units cost USD 1-7.5 million (2011 prices, since up about 75%) and take up to four years to obtain | AC only; heavy; supply bottlenecks | Design life about 40 years; some units run over 70 |
| **Amorphous-core distribution transformer**^[2](https://www.energy.gov/node/4839605) | Lowest no-load losses | Distribution sizes | DOE's 2024 rule leaves about 75% of the US market able to comply with grain-oriented steel; the draft would have moved about 95% to amorphous | Bulkier, limited supply | Comparable to conventional units |
| **Rectifiers**^[11](https://www.advancedenergy.com/en-us/about/news/blog/steel-manufacturing-requires-efficient-electric-arc-furnaces/) | High; thyristor controllers approach 99.5% (supplier claim, arc-furnace context) | Watts to gigawatts | Mature, low cost per kW | Draw distorted (harmonic) currents unless filtered | Few moving parts; cooling is the weak point |
| **Inverters and variable speed drives**^[5](https://www.energy.gov/sites/prod/files/2014/04/f15/motor_tip_sheet11.pdf)^[7](https://www.woodmac.com/press-releases/solar-inverter-ranking-h1-2025/)^[14](https://www.woodmac.com/es/press-releases/global-pv-inverter-shipments-grew-by-10-in-2024-to-589-gwac/) | Drives 95-97% at full load | Microinverters of a few hundred watts to central inverters of several MW | Highly competitive; Huawei and Sungrow shipped about 55% of 2024 PV inverters | Efficiency drops at very light load; capacitors and fans age | Top solar makers offer warranty extensions of 20 years or more |
| **DC-DC converters** | No single published figure found | Milliwatts to hundreds of kW | Commodity electronics | Heat in compact packages | Capacitor ageing |
| **EV chargers**^[9](https://www.utilitydive.com/news/electric-vehicle-ev-aspirations-will-require-rapid-charging-buildou-NREL/684940/)^[15](https://avt.inl.gov/sites/default/files/pdf/presentations/INL_DCFastChargerInfrastructure.pdf)^[18](https://investors.kempower.com/wp-content/uploads/sites/2/2026/05/kempower-capital-markets-day-2026-presentation.pdf) | 92.3% AC to DC measured on a 50 kW unit (INL, 2016); no independent figure found for newer silicon carbide units | A few kW (home) to 350 kW and above (fast) | Up to about USD 240,000 per public DC fast port and USD 11,000 per public Level 2 port (calculated from NREL upper-bound totals) | Grid connection cost and delay | Kempower reports over 99% uptime for its units (company claim); no independent figure found |

Transformers are the most efficient and longest-lived, but bulky and now supply-constrained. Power electronics are more flexible (any frequency, DC or AC, precise control) and shrinking fast as silicon carbide replaces silicon, but they age faster because of capacitors, fans and thermal cycling, and lose efficiency at very light loads. In most systems both appear together: a transformer to set the voltage and a converter to set the form.

#### How each method works
**Power and distribution transformers**

Two or more windings on a laminated iron core change AC voltage by the turns ratio. Large units are oil-filled; distribution units sit on poles and pads.
**Amorphous-core distribution transformer**

Replaces grain-oriented steel with a thin, non-crystalline metal ribbon that magnetises with less loss.
**Rectifiers**

Diodes or thyristors let current flow one way only, turning AC into DC for electrolysers, smelters, data centres, chargers and HVDC links.
**Inverters and variable speed drives**

Transistor bridges switch DC to make AC of any frequency, for solar and batteries feeding the grid, motor drives and EV traction.
**DC-DC converters**

Switch and smooth DC to raise or lower its voltage, for example between a car battery and its 12 V system or in phone and laptop supplies.
**EV chargers**

AC (Level 1 and 2) chargers pass grid AC to the car's onboard rectifier; DC fast chargers contain their own rectifier and converter to feed the battery directly.

#### Sources

1. [Building the Future Transmission Grid: executive summary](https://www.iea.org/reports/building-the-future-transmission-grid/executive-summary) International Energy Agency, 2025
2. [DOE Finalizes Energy Efficiency Standards for Distribution Transformers (press release, 4 April 2024)](https://www.energy.gov/node/4839605) US Department of Energy, 2024
3. [Large Power Transformers and the U.S. Electric Grid](https://www.energy.gov/sites/prod/files/Large Power Transformer Study - June 2012_0.pdf) US Department of Energy, Office of Electricity, 2012
4. [Transforming revenue (ABB Review 2/2015)](https://library.e.abb.com/public/929bc703922d49069e6920d5ce6ab9c1/53-57%202m522_EN_72dpi.pdf) ABB, 2015
5. [Adjustable Speed Drive Part-Load Efficiency, Motor Systems Tip Sheet #11](https://www.energy.gov/sites/prod/files/2014/04/f15/motor_tip_sheet11.pdf) US Department of Energy, 2012
6. [Global solar inverter manufacturer ranking H1 2025](https://www.woodmac.com/press-releases/solar-inverter-ranking-h1-2025/) Wood Mackenzie, 2026
7. [EV aspirations will require rapid charging buildout: NREL (reporting NREL, The 2030 National Charging Network, 2023)](https://www.utilitydive.com/news/electric-vehicle-ev-aspirations-will-require-rapid-charging-buildou-NREL/684940/) Utility Dive, 2023
8. [Steel manufacturing requires efficient electric arc furnaces](https://www.advancedenergy.com/en-us/about/news/blog/steel-manufacturing-requires-efficient-electric-arc-furnaces/) Advanced Energy, 2023
9. [Large Power Transformer Resilience: Report to Congress](https://www.energy.gov/sites/default/files/2024-10/EXEC-2022-001242%20-%20Large%20Power%20Transformer%20Resilience%20Report%207-10-24.pdf) US Department of Energy, 2024
10. [Global PV inverter shipments grew by 10% in 2024 to 589 GWac (press release, 10 July 2025)](https://www.woodmac.com/es/press-releases/global-pv-inverter-shipments-grew-by-10-in-2024-to-589-gwac/) Wood Mackenzie, 2025
11. [DC fast charger infrastructure testing (ABB Terra 53 efficiency)](https://avt.inl.gov/sites/default/files/pdf/presentations/INL_DCFastChargerInfrastructure.pdf) Idaho National Laboratory, 2016
12. [Kempower Capital Markets Day 2026 presentation](https://investors.kempower.com/wp-content/uploads/sites/2/2026/05/kempower-capital-markets-day-2026-presentation.pdf) Kempower, 2026

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_power_electronics/index.md)
- [Overview](https://www.materialinsights.org/energy/e_power_electronics/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_power_electronics/correlation/index.md)
- [Science and limits](https://www.materialinsights.org/energy/e_power_electronics/science/index.md)
- [Value chain](https://www.materialinsights.org/energy/e_power_electronics/valuechain/index.md)
- [Unit economics](https://www.materialinsights.org/energy/e_power_electronics/economics/index.md)
- [Equipment and suppliers](https://www.materialinsights.org/energy/e_power_electronics/equipment/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_power_electronics/links/index.md)