A power transformer is the quiet workhorse of every electrical network. It steps voltage up for efficient transmission and back down for safe distribution, moving energy from the generating plant to the factories, buildings, and homes that use it. This guide from Kampa Electric explains what a power transformer is, how it works, the main types you will meet, and how to choose the right one for a project.
A power transformer is a static electrical device that transfers alternating-current power between two or more circuits at different voltage levels through electromagnetic induction. It has no moving parts, which is why it can run for decades with little more than routine maintenance. In distribution networks, a power transformer steps medium voltage down to a usable low voltage; in transmission networks, it steps generation voltage up to reduce losses over long distances.
A power transformer works on Faraday’s law of electromagnetic induction. An alternating current in the primary winding produces a changing magnetic flux in the laminated core. That flux links the secondary winding and induces a voltage in it. The ratio between the primary and secondary voltages is set by the ratio of their turns, so the same device can step voltage up or down depending on which side is connected to the source.
Because the windings are magnetically coupled rather than electrically connected, a power transformer also provides isolation between the primary and secondary circuits. This is a core part of why transformers are central to grid safety and reliability.
Power transformers are grouped by their insulation and cooling method, and by where they sit in the network. The table below summarizes the common categories.
| Type | Cooling / insulation | Typical use |
|---|---|---|
| Oil-immersed transformer | Insulating oil | Outdoor substations, utilities, high-capacity distribution |
| Dry-type transformer | Air / solid insulation | Indoor, fire-sensitive sites, commercial buildings |
| Distribution transformer | Oil or dry | Final voltage step-down to the end user |
| Power transformer (transmission) | Oil | High-voltage transmission and substations |
For most industrial, commercial, and utility distribution projects, the Oil Immersed Distribution Transformer is the dependable default. It uses insulating oil for both insulation and cooling, giving it strong overload capacity, stable heat dissipation, and long service life in outdoor installations.
Choosing the right power transformer comes down to a handful of parameters that must match the project:
The SCB Series Epoxy Resin Dry Type Transformer suits indoor, fireproof installations, while the Dry Type Transformer Insulation Series and the 35kV Oil Immersed Power Distribution Transformer cover the wider range from indoor commercial to medium-voltage utility distribution. You can browse the full lineup on the products page.
Power transformers appear wherever voltage must change level in a power system:
A power transformer is a static device that transfers AC power between circuits at different voltage levels through electromagnetic induction, used to step voltage up or down in transmission and distribution networks.
A power transformer is used at higher transmission voltages for bulk transfer, while a distribution transformer performs the final step-down to the voltage the end user actually uses.
Oil-immersed transformers use insulating oil for cooling and insulation and suit outdoor and high-capacity use; dry-type transformers use air or solid insulation and suit indoor, fire-sensitive locations.
It is rated in kVA (or MVA for large units) because the apparent power it carries includes reactive load, which watts alone do not capture.
Rated capacity, primary and secondary voltage, frequency, phase, connection group, impedance, cooling method, installation environment, and order quantity.
A power transformer does one essential job — change voltage safely and efficiently — and the right choice depends on matching capacity, voltage, cooling, and application. For more about the manufacturer behind this range, see our about us page, or contact us to discuss specifications and request a quotation for your project.
