Electrical Transformer Basics

The purpose of an electrical transformer is to convert current from one electrical circuit to another, while maintaining the same frequency. This can be done as an increase in voltage and current, or a decrease.

Because of the wide variety of applications for them, transformers come in many different sizes and configurations. In fact, some can be as tall as a small office building, while others can fit into the palm of your hand.

Here, we’ll review some electrical transformer basics.

How Transformers Are Constructed

Rather than generate power, these devices transfer it using magnetic coupling from one circuit to another. The four basic parts of a transformer are the Input Connection, the Output Connection, the Windings (or Coils) and the Magnetic Core.

The input connection is termed the primary side because it is where power enters the device. The secondary side — or output connection — is where power exits after the transformation is complete.

The core is the path connecting the two windings, which conducts the magnetic flux generated by the current. Windings can surround the outside of the core (core transformers) or be placed within it (shell transformers).

How Transformers Work

Voltage enters the device and incites the flow of current in the primary winding. This sets up a magnetic field in the core, which produces alternating voltage in the secondary winding. The variance between input and output voltage is determined by the number of turns of wire in each winding. It also defines whether the transformer will step voltage up or decrease it.

When the secondary winding has more turns than the primary, output voltage is increased (stepped up). When the primary has more turns, voltage is stepped down. Thus, the ratio between the number of turns between the two windings can define both the type and the output of a transformer.

Transformer Types

Step-up vs. Step-down – Step-up transformers are usually found within power plants, while step-down transformers are generally used in transmission and distribution systems. Thus, both are required to get electricity from the power plant to the end user.

Single-Phase vs. Three-Phase – Electrical transformers using one set of windings are known as single phase. When three sets of windings are combined in one device it becomes a three-phase transformer. Configured for heavier duty, three-phase transformers are typically deployed for the generation, transmission and distribution of power in industrial settings.

Power vs. Distribution

– Power transformers couple electrical energy from power supply line circuit systems, such as from the generation station to the pole outside your home. Distribution transformers are used to couple power from the pole into your home. In other words, power transformers are employed to conduct electricity; while distribution transformers (as their name implies) are used to distribute it.

Oil-Filled vs. Water-Cooled Oil Filled vs. Air Cooled

Heat is a natural by-product of the functioning of a transformer. This means some form of cooling must be employed to ensure their reliability and longevity.

Smaller transformers of up to three MVA typically are filled with oil to facilitate cooling. Water-cooled oil-filled transformers are usually larger and add water-cooling to enable a more effective transfer of heat from the oil. Air is forced over the windings and the coil to displace heat in an air-cooled configuration.

As detailed as all of this is, it’s just the tip of the iceberg when it comes to completely understanding transformers. Essential to the operation of electrical systems as well as electronic devices, transformers are key to electricity management.

Hopefully, the primer on electrical transformer basics helped you gain a fundamental understanding of how these critical components do their jobs. Electrical systems as we know them could not function as efficiently without transformers.

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