General Types of Transformers

Transformers are more than just extraterrestrial robots—they’re also highly useful devices for transferring energy between circuits. By using inductively coupled electrical conductors as the main agent of transfer, a change in current in the first circuit is carried over to the second circuit, which subsequently assumes the new charge. Each end of the circuit carries the charge within a winding—either primary or secondary—which is constituted of electrically conductive wire wound around opposite ends of the transformer core, which has high magnetic permeability, making the transfer possible.

In an ideal situation, the change in voltage is proportional, with the second circuit receiving voltage in relation to the number of turns in the primary winding. The voltage is therefore manipulated by altering the number of turns in the primary winding to be larger or smaller than the number of turns in the secondary winding, which either increases or decreases the amount of electricity received.

Transformers are essential when it comes to the national power grid and are responsible for transmitting large amounts of high voltage power over long distances. This is not to say that all transformers are large—they come in many different sizes—and some are certainly not designed for high levels of output. Depending on the intended function and the amount of power needed, transformers can be as small as a fingernail or weigh several hundred tons.

Common Types of Transformers

AutotransformersDiagram of an Auto-Transformer

Autotransformers are different from traditional transformers because autotransformers share a common winding. On each end of the transformer core is an end terminal for the winding, but there is also a second winding that connects at a key intermediary point, forming a third terminal. The first and second terminals conduct the primary voltage, while the third terminal works alongside either the first or second terminal to provide a secondary form of voltage. The first and second terminals have many matching turns in the winding. Voltage is the same for each turn in the first and second terminal. An adaptable autotransformer is another option for this process. By uncovering part of the second winding and using a sliding brush as the second terminal, the number of turns can be varied, thus altering voltage (see image on right).

Polyphase Transformers

This type of transformer is commonly associated with three phase electric power, which is a common method of transmitting large amounts of high voltage power, such as the national power grid. In this system, three separate wires carry alternating currents of the same frequency, but they reach their peak at different times, thus resulting in a continuous power flow. Occasionally these “three-phase” systems have a neutral wire, depending on the application. Other times, all three phases can be incorporated into one, multiphase transformer. This would require the unification and connection of magnetic circuits so as to encompass the three-phase transmission. Winding patterns can vary and so can the phases of a polyphase transformer.

Leakage Transformer

Leakage transformers have a loose binding between the primary and secondary winding, which leads to a large increase in the amount of inductance leakage. All currents are kept low with leakage transformers, which helps prevent overload. They are useful in applications such as arc welding and certain high-voltage lamps, as well as in the extremely low-voltage applications found in some children’s toys.

Resonant Transformer

As a type of leakage transformer, resonant transformers depend on the loose pairing of the primary and secondary winding, and on external capacitors to work in combination with the second winding. They can effectively transmit high voltages, and are useful in recovering data from certain radio wave frequency levels.

Audio Transformer

Originally found in early telephone systems, audio transformers help isolate potential interference and send one signal through multiple electrical circuits. Modern telephone systems still use audio transformers, but they are also found in audio systems where they transmit analog signals between systems. Because these transformers can serve multiple functions, such as preventing interference, splitting a signal, or combining signals, they are found in numerous applications. Amplifiers, loudspeakers, and microphones all depend on audio transformers in order to properly perform.