Power is generated and transmitted at high voltage but used at much lower voltage, and matching one to the other is the job of the transformer. With no moving parts, it changes an AC voltage from one level to another through magnetic coupling between two coils. This guide explains what a transformer is, how mutual induction and the turns ratio set the output voltage, the difference between step-up and step-down units, and where transformers sit in oil and gas power systems.
Transformer in one line: A transformer is a static electrical device that transfers AC energy between two or more windings through electromagnetic induction, changing the voltage in proportion to the ratio of turns on each winding. It steps voltage up for efficient transmission or down for use, without changing the frequency, and with no rotating parts.
A transformer has a primary winding and a secondary winding wound on a shared iron core. Alternating current in the primary sets up a changing magnetic flux in the core, and that changing flux induces a voltage in the secondary. Because both windings link the same flux, the induced voltages are proportional to the number of turns: the secondary voltage equals the primary voltage times the turns ratio (secondary turns divided by primary turns).
Ideally the transformer conserves power, so as voltage steps down, current steps up in the same proportion, and vice versa. A transformer only works on AC - it needs the continuously changing flux. It changes voltage and current but not frequency. Real transformers have small losses from winding resistance, core hysteresis, and eddy currents, which is why larger units are often oil-filled and cooled.
A step-up transformer has more turns on the secondary than the primary, so it raises voltage - used at generation to push power onto transmission lines efficiently, since higher voltage means lower current and lower line losses. A step-down transformer has fewer secondary turns and lowers voltage - used at substations and facilities to bring transmission or distribution voltage down to usable levels.
The same physical transformer can often be used either direction; step-up and step-down simply describe how it is connected in the system. Three-phase power uses three-phase transformers (or three single-phase units) with delta or wye winding configurations that also shift the phase and provide or omit a neutral. Tap changers let the turns ratio be adjusted in steps to hold output voltage steady as load or supply voltage varies.
Oil and gas facilities receive power at distribution or transmission voltage and step it down through one or more transformers to the 480 V or 600 V used by motors and MCCs, and further to 120/240 V for controls, lighting, and instruments. Padmount and pole-mount distribution transformers are common at well pads and remote sites; larger power transformers appear at plants and compressor stations. Specialized units feed VFDs and electric submersible pumps.
Larger transformers are monitored for oil temperature, winding temperature, oil level, and gas accumulation (a sign of internal faults), often through sensors and Buchholz relays wired to a controller. A cloud SCADA such as Merobix can read those transformer temperature and status tags over Modbus or DNP3, so an operator sees loading and any thermal or fault alarm on remote transformers alongside the rest of the site.
It uses two coils on a shared iron core. AC in the primary creates a changing magnetic flux that induces voltage in the secondary. The output voltage is set by the turns ratio: more turns on the secondary steps voltage up, fewer steps it down. Only voltage and current change - the frequency stays the same.
A transformer relies on a continuously changing magnetic flux to induce voltage in the secondary. AC provides that changing flux naturally. Steady DC produces a constant flux that induces no secondary voltage, so a plain transformer cannot step DC up or down - that requires switching electronics like a DC-DC converter.
A step-up transformer raises voltage (more secondary turns) and is used to send power onto transmission lines efficiently. A step-down transformer lowers voltage (fewer secondary turns) to bring it to usable levels at a facility. The terms describe how the unit is connected in the system, not a different kind of transformer.
This page references the protocol specifications published by the organizations below. Editions, product capabilities, and documentation change over time - confirm current requirements and specifications directly with the source.
Last reviewed: July 27, 2026. Merobix is not affiliated with, endorsed by, or sponsored by these organizations; their names are used only to identify the standards and products discussed.
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