A device specifically designed to change the voltage of an alternating current (AC) supply is called a transformer. Transformers are fundamental to the operation of modern electrical power systems, serving as pivotal components in the generation, transmission, and distribution of electrical energy.
At its core, a transformer operates on the principle of electromagnetic induction, which was discovered by Michael Faraday in the early 19th century. This principle states that a change in magnetic field within a closed loop of wire induces an electromotive force (EMF) in the wire.
A basic transformer consists of two coils, often referred to as the primary and secondary coils, wound around a shared iron core. When alternating current flows through the primary coil, it produces a changing magnetic field around it. This changing magnetic field, in turn, induces a voltage in the secondary coil. By adjusting the number of turns in the primary and secondary coils, one can determine the voltage increase or decrease. For instance, if the secondary coil has more turns than the primary coil, the output voltage (on the secondary side) will be higher than the input voltage (on the primary side), and the transformer is called a step-up transformer. Conversely, if the secondary coil has fewer turns, the transformer will reduce the voltage, making it a step-down transformer.
Apart from voltage transformation, transformers also provide electrical isolation between circuits, which can be vital for safety and functional reasons.
Large power transformers, often seen in substations, play a critical role in the electrical grid. They adjust the voltage levels from high-voltage transmission lines (for efficient long-distance transport) down to levels suitable for local distribution. There are also many smaller transformers in everyday use, such as those in electronic devices and appliances, adapting voltages to specific needs.
It’s worth noting that while transformers are incredibly efficient, they are not 100% efficient. Some energy losses occur, mainly due to resistive heating in the coils and hysteresis and eddy current losses in the core. However, advancements in design and materials over the years have optimized transformer efficiency to a great extent.