Electrical transformers help make modern life possible, but many people are unsure of how they work and what they do. Everything from laptop chargers to industrial machines need transformers in their electrical system, and most modern technology would cease to exist without these devices. Here is a look at the basics of how a transformer works and some of the most common types of transformers used today.
Electrical Transformers: A Quick Overview
The electricity that is transported through the power grid is actually not usable in most situations without transformers. Research has shown that high voltage electricity is much more efficient when moving through wires, but most modern devices cannot operate at particularly high volts. The basic job of a transformer is to alter the voltage up or down without changing the frequency. Large transformers are often seen along power lines, but smaller transformers can be found in vehicles, smartphone chargers, heavy machinery, and countless other devices.
Before delving into the most common types of transformers, it is important to understand some of the basic principles that allow them to work. Transformers are comprised of a primary wire, a secondary wire, and a core. The primary wire has a current running through it, and this produces a magnetic field due to electromagnetic induction. The core then transfers this energy to the secondary wire without changing the frequency of the energy. By altering the shape of the wires and their magnetism, the voltage can either be increased or decreased.
Autotransformers are unique in the fact that they share a common winding. The winding meets at various terminals throughout the transformer to produce a similar voltage where the wires have an identical turn. An adaptable autotransformer is another unique option with a sliding brush placed along a second winding to create another terminal. This allows the transformer to quickly alter the turns of the wire, thus altering the voltage that is produced.
Also referred to as three-phase transformers, these transformers are most often seen where huge amounts of energy must be transferred such as larger power grids. Instead of just one or two windings, these transformers have three windings with three separate currents at the same frequency. The output energy comes in alternating phases as the windings peak at different times. What this allows the transformer to do is provide a consistent power flow without changes to the energy output. Polyphase transformers with windings that peak at the same time are referred to as multiphase transformers.
As their name implies, leakage transformers allow some of the energy to leak away from the windings. This takes place because there is a very loose binding between the first and second winding. Due to the leakage, the current must be kept very low for these transformers in order to avoid serious damage from an overload. Interestingly enough, this overload can be used for practical purposes such as arc welding, but it is typically used for smaller toys and electronics.
The primary purpose of a power transformer is to alter the voltage of electricity moving from a power line to one or more circuit systems. When used on a solid-state circuit system, this type of transformer is referred to as a rectifier transformer. A power transformer is generally rated by the maximum voltage and current capacity that it is capable of producing.
An isolation transformer is actually one of the most unique transformers because the wiring has a 1:1 turn ratio. Unlike a step up or step down transformer, the voltage that is moving between the two wires is nearly identical. This isolates the grounded conductor of the primary power line from all other components. While there is still a danger of shocking if physical contact is made between the primary and secondary winding, these transformers are designed to be as safe as possible. It is an interesting fact that all transformers technically isolate the grounded conductor, but this term is generally only applied to transformers that are purposefully designed to isolate the circuits.
Out of all the types of transformers that exist today, the potential transformer is often seen as the most delicate as well as the most accurate. A potential transformer’s only job is to lower the voltage by a small and extremely accurate amount. Some of the most common transformation ratios for this style of transformer are 10:1, 20:1, and 40:1. Potential transformers are almost always shell type transformers because they have been found to be much more accurate than core type transformers.
What makes instrument transformers so interesting is the fact that they are only placed inside devices such as voltmeters that are used to test other currents. Also referred to as accurate ratio transformers, this device transforms the voltage at a very specific ratio so that incoming currents can be tested. An instrument transformer can generally only handle a small amount of power (load) because of the delicate moving elements.