What is the difference between 'Step-up and Step-down' Transformers?

What is the difference between 'Step-up and Step-down' Transformers?

2022-10-18

For anyone wanting to understand the differences between step-up and step-down transformers perhaps the first thing to understand is the purpose of these pieces of equipment.

Power transformers are machines that enable the transfer of electricity from one circuit, or place, to another and which also change the voltage. Designed solely for use with an alternating current supply the fact that they work with an AC means that where there is a change in the voltage this will also affect the current, and vice versa.

One of their primary functions is as a safety device that also increases energy efficiency which they achieve by raising and lowering voltage levels when necessary. As we shall see, this is where the step-up and step-down classifications come in.

You will find transformers of both kinds used in many industrial locations and one of their key roles is to safely regulate and distribute electrical power over a wide range of distances.

The construction of a transformer

Any transformer has three major components: these are a magnetic core and primary and secondary windings. The primary winding is connected to the power source from where magnetic flux is produced. The magnetic core then relays the flux to the secondary winding to create a powerful magnetic circuit.

A transformer actually works because it follows Faraday’s law of electromagnetic induction that states: “the rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil”.

The use of an alternating voltage to the primary winding creates an alternating flux in the core which links both windings to induce EMF on both the primary and secondary sides. EMF in the second one creates a current, called the load current, as long as there is a load connected to the secondary section.

This process changes the voltage level as required, but not the frequency.

Transformers are fairly efficient as there are no moving parts to cause friction, but there are some losses as the current passing around the wiring does heat it up. There is also a similar form of heat loss in the core. As many transformer manufacturers have discovered, the losses can be considerably reduced through the use of special steel alloys.

Typical uses of transformers

In an industrial setting, there are a number of typical uses for transformers of both the step-up and step-down varieties. These include:

• The raising or lowering of the voltage level in an alternating current circuit

• Increasing or decreasing the value of an inductor or capacitor in an alternating current circuit.

• Preventing the passage of a direct current from one circuit to another.

• Isolating two electrical circuits.

• Stepping up the voltage level at the site of power generation before the transmission and distribution can take place.

Step-up transformers

As the name suggests, in a step-up transformer the voltage is increased on the output side.

In this, the number of turns in the secondary winding is always more than in the primary winding and this is how the higher voltage can be developed before leaving the transformer.

In a step-up transformer, the primary winding is made using thick insulated copper wire while the secondary winding uses a much thinner wire. However, in a step-down transformer, the output current is high so it is the thick insulated copper wire that is always used for making secondary winding.

One of the main reasons for wanting to raise the voltage is when AC power needs to be transmitted over long distances, such as in certain areas of the National Grid. Another useful by-product of this is that the current reduces as the voltage rises. This results in a decreased level of heat loss and therefore increases efficiency.

Step-down transformers

When it comes to distributing electricity to different areas there is also always going to be the need to step the voltage down for safety reasons. This is achieved by having fewer turns on the secondary winding than on the primary winding. The result of this is that a smaller voltage is induced at the output end of the transformer.

Switching the kind of transformer

It’s also interesting to know that the same transformer can be used as either a step-up or a step-down one. This is simply achieved by changing the input of the source power from the primary to the secondary winding, or vice versa.

Types of transformers

Leading transformer manufacturers such as GBE SPA and UK will also offer a number of different types of transformers.

For example, they provide a range of “dry type” pieces of equipment. In these, the coils are either cast in, or insulated within, encapsulating resin.

The other main type is known as an oil transformer. In this, the magnetic core and windings are fully immersed in a non-conducting liquid like silicone or even biodegradable fluids. The type of oil generally relates to the precise use of the transformer and the nature of its installation. Other considerations include the safety measures needed and general environmental restrictions.

So we hope this article has increased your understanding of not just step-up and step-down transformers, but the uses and purpose of transformers in general.

For more information, or to discuss how we can meet your transformer needs, please just get in touch.