All electrical devices need a source of electricity in order to work, but it needs to be the correct size and rate. A small household device, for example, doesn’t need the kind of high voltage electricity that is sent down power lines over long distances. To be able to use electricity in everyday applications, therefore, electrical current passes through a transformer first.
Understanding the basics of what a transformer is
A transformer converts electrical current into a suitable voltage, so it is an electrical device which takes an input voltage and changes it into a different output voltage. This will only work with alternating current (AC), but can increase the voltage as well as decrease it. So these are known as step-up transformers, which increase voltage, and step-down transformers, which decrease the voltage.
To understand how transformers work, we can use a comparison to water flow, but first let’s look at some basic definitions:
Current = the rate of flow of electrical energy, which is measured in amps
Voltage = the force of electrical energy, which is measured in volts
So if we compare electrical energy to a water system, current is equal to how fast the water flows through pipework, and voltage can be compared to the water pressure that is received at the point of use. Transporting water around the civil system requires the management of pipe length and size along with water pressure to ensure the volumes of water and the water pressure received is appropriate to each individual need. So an industrial business which requires water for production processes, for example, needs large volumes at high pressure, while a household kitchen sink requires only small volumes at relatively low pressure. The water system is designed and managed to serve these needs, and transformers essentially do this same job for the electricity system, to make electrical current usable at the point of use.
How do transformers work?
A transformer doesn’t make electricity, it simply changes the voltage according to the needs of the user. It does this through a process called electromagnetic induction. If you run an alternating current through a wire (which we will call a conductor) it creates an invisible magnetic field around the wire/conductor. If you placed a second conductor within this magnetic field, the moving flux lines inside this field will induce a current in the second conductor, and we can use this electromagnetic induction to increase or decrease the voltage between the two conductors.
Changing the voltage between two conductors is achieved by wrapping the two conductors into coils, with one coil being shorter than the other. The coil with more loops is then electrified, and the current induced in the coil with fewer loops will be lower than the current seen in the first coil. The first coil conductor is known as the primary conductor and the second coil where current is induced is known as the secondary coil.
We can therefore build a transformer to achieve the exact output voltage we need by understanding a simple rule of ratios. The ratio of loops between the primary coil and the secondary coil will determine the ratio of the voltage between the coils. So to build a transformer with the exact ratio we need, we simply apply the ratio to the primary and secondary coils. For example, if we built a transformer with a 25:1 ratio of loops between the two coils, we could achieve a step-down voltage from an input voltage of 12,000 volts to an output voltage of 480 volts.
Please note that this section is for information purposes only. Anyone using equipment referred to in this section must be suitably qualified and/or experienced within the respective field. If in doubt before use, please consult a qualified electrician or engineer & thoroughly read all instruction booklets.