Electric motors, streetlamps, data centers, stadiums and other similar structures dependent on electricity need immediate access to substantial electricity. However, obtaining electricity for a specific application is not as straightforward as merely connecting to the power lines. High voltage electricity in power lines is exclusively appropriate for long-distance power transmission. For practical applications, electricity must travel through a transformer that adjusts its power to the required voltage.

Similarly, industries have large production machines that rely on electricity for operation. The voltage an appliance requires is proportional to the amount of energy it consumes. Therefore, equipment that consumes a lot of power may utilize 1,000 V to 10,000 V rather than 110 V to 250 V. Mostly, 400 V are sufficient for smaller manufacturing facilities and machine shops. Therefore, it is imperative to note that various electrical consumers necessitate the usage of different voltages as per their needs. Practically, shipping high-voltage power from the power station and later converting it to lower voltages at each destination makes sense. This is because stepping up the voltage reduces current, which in turn minimizes I²R losses (resistive losses) in transmission lines. All of this is possible because of transformers that will be discussed in this article.

What is a transformer?

To put it simply, a transformer is a device that increases or decreases the voltage. A step-down transformer reduces the output voltage whereas a step-up transformer raises it. To maintain a constant relationship between the system's input and output power, a step-down transformer will raise the output current and a step-up transformer will lower it.

In the transmission and distribution of alternating current power, the transformer plays a crucial role as a voltage control device. Many other notable scientists have built on Michael Faraday's (1831) work to develop the concept of a transformer. But in general, transformers were used to keep the low-voltage electricity consumption in check with the high-voltage electrical generation.

How does a transformer work?

The theory of electromagnetic induction and mutual induction forms the basis of the transformer's operation.

The core of a transformer typically contains two coils: the primary coil and the secondary coil. A substantial mutual inductance exists between the two coils, and there is complete electrical separation between the two. The magnetic core travels through the main winding and is connected to the secondary winding through low reluctance, which serves to maximize the connection or link. A changing magnetic flux is produced when an alternating current flows through the main coil. This change in magnetic flux generates an electromotive force (EMF) in the secondary coil, which is magnetically connected to the core by a primary coil, in accordance with Faraday's law of electromagnetic induction. What we see here is an example of mutual induction. The magnitude of the electric current is proportional to the magnetic flux density.

In general, the transformer works by abiding the following principles:

1. Power transmission using electromagnetic induction

2. Power transmission from one electrical circuit to another

3. Transmission of electric power with constant frequency

4. There can be no difference between the input and output power levels.

5. Mutual induction connects two circuits.

6. The primary coil and secondary coils are linked magnetically but electrically are not coupled.

7. Transformers work only with alternating current because the magnetic field must vary to induce a voltage.

Types of transformers

Transformers come in many forms, each suited for different applications:

1. Power transformers:
   • High-power units used in electrical grids to step-up or step-down voltage levels. They operate at high voltages (up to hundreds of kV).
   • Found in substations, they enable long-distance power transmission with minimal losses by increasing the voltage and reducing the current.
2. Distribution transformers:
   • Step down the voltage from the transmission lines to a level suitable for home and commercial use.
   • Typically mounted on poles or placed in substations near the end user.
3. Instrument transformers:
   • These transformers are used to measure voltage or current levels. They include:
     • Current transformers (CTs): Used to reduce high current to a lower, measurable value.
     • Potential transformers (PTs): Reduce high voltage to measurable levels for metering and protective relays.
4. Isolation transformers:
   • Primarily used to isolate circuits for safety, often in sensitive equipment or for fault protection.
   • They provide no direct electrical connection between the input and output, helping prevent electrical shocks and interference.
5. Autotransformers:
   • Unlike a standard transformer, the primary and secondary windings share part of the same coil. This design is more efficient for small voltage changes but lacks electrical isolation.
6. Step-up and step-down transformers:
   • Step-up transformers increase voltage from a lower voltage source, used in power plants.
   • Step-down transformers decrease voltage to usable levels, typically found near homes and industries.

Conclusion

A transformer uses electromagnetic induction to move electrical energy from one circuit to another. It is essential in the transmission and distribution of electrical energy since its primary role is to step up or step-down voltage levels while maintaining a constant power. They adjust the current accordingly with the voltage so that the overall power remains constant (excluding minor losses). However, in real transformers, there are always some losses (like core losses, copper losses, etc.), so the actual power output is slightly less than the input power.