What are transformers?

Transformers - sadly we're not referring to the robots in disguise - are devices used to change the voltage of an electric current. Transformers are either used to increase (known as “stepping up”) or decrease (known as “stepping down”) the voltage of a current. They are particularly important in long distance power transmission, to convert the voltage from one that is safe for human use to a higher voltage that is more efficient for transmission, and to convert it back again. Transformers are often used to adjust the voltage of the distribution current to a voltage that suits the specific application of the device (the power brick of a laptop, for instance, includes a transformer to step down the voltage before converting the current from AC to DC). 

The principle of transformers relies on Faraday’s laws of induction, which describe how when current flows through one electrical coil it can create – or induce – a current in a coil placed nearby. To maximise the effectiveness of this induction, in a transformer the coils are both wrapped around a piece of metal known as the core. By changing the number of turns on the second coil, the voltage of the induced current is changed – if the second coil has more turns than the primary coil, the voltage will increase, and vice versa. Transformers generate heat and so require cooling; smaller transformers (such as those in laptop power bricks) make do with air cooling, while larger transformers use a special kind of oil, or another liquid-filled system, to remove heat from the system. 

As transformers are an important part of power transmission networks, it’s important that they are connected using cables that are able to withstand the rigours of use. That includes being resistant to environmental conditions (since many high voltage transformers are outdoors to reduce the risk of arcing), and being able to handle the correct voltage.