110V vs 240V Power Tools. Different Types of Transformers

Last updated: December 14, 2022

We’ve all had the experience of purchasing a basic corded power tool and determining whether a 110V or 240V tool is required. The voltage at which 110V and 240V electric tools operate is the primary distinction. Both versions produce the same amount of power and perform the same tasks. On the UK market, both 110V and 240V are available, primarily for health and safety reasons.

110V vs 240V Power Tools

You should be aware that 240V power tools are compatible with standard three-pin domestic plug sockets in the UK and are ideal for use around the house and in the DIY workshop. While 110V power tools are designed for heavy-duty construction site use, and they require a transformer to function.

240V to 110V Transformer

A 240V to 110V transformer converts a standard 240V power supply to 110V, which is then connected via leads to your power tools.

These transformers are composed of two 55V lines that combine to create a 110V power supply, which is a much safer voltage to work at in the event of an accident.

It is not required by law (in the UK) to use a 110V supply on the job site, but it is advisable. 240V power supplies are not recommended for on-site jobs due to health and safety concerns.

Sealey WST3000 Portable Transformer 3000VA

Sealey WST3000 Portable Transformer

Draper 31264 3.3kVA 230V to 110V Portable Site Transformer

Draper 31264 3.3kVA 230V to 110V Portable Site Transformer

Types of Transformers

Power Transformers

Power transformers are devices that transfer electricity from a generator to the distribution primary circuits. Sometimes it can get a little confusing because many people use the term “power transformer” to refer to a group of transformers rather than a specific design type. Similarly, some people refer to large transmission transformers as power transformers to distinguish them from distribution transformers.

Power transformers have three main functions:

  1. Step-up generator output voltage to transmission system voltage level.
  2. Step down transmission voltages to safe levels for distribution.
  3. Step down the voltage to the auxiliary power system level in a generating station.

Power transformers fall into two classes:


Autotransformers are large power transformers, but they are typically used as transmission inter-tie transformers that can operate in either step-up or step-down mode. An inter-tie transformer connects AC networks of different voltages, a critical feature in a power network.

Because there is a physical connection between the series and common windings, they are more cost-effective than having separate winding power transformers.

However, autotransformers have one drawback: low impedance. An autotransformer’s short circuit current is much higher than a conventional transformer due to its low impedance. To counteract this, autotransformers are typically designed with a higher-than-normal impedance, which simply increases the unit’s overall size, contradicting the previously mentioned benefit.

Generator Step-Up Transformers (GSUs)

GSUs (also known as main or unit transformers) increase the voltage from a generator to the maximum transmission voltage for a transmission grid. GSUs are typically operated at a constant load close to their full rating when connected directly to the generator. They will age much faster than other transformers because they constantly operate at their rated temperature.

Because GSUs aren’t usually protected by a circuit breaker between the generator and the transformer, they can also be hit pretty hard with fault current (and for long periods of time), resulting in massive overvoltages. If a generator breaker is used, a GSU can actually be used to power the auxiliary systems of a grid.

Auxiliary Transformers

Auxiliary transformers provide power to the auxiliary loads of a power plant (feed pumps, coolant pumps, and safety devices that a power plant needs to run). There are a few different types of auxiliary transformers:


In the case of converting 240V to 110V power for the use of power tools, a step-down transformer is required to reduce voltages to safe levels for distribution. An inter-tie autotransformer, for example, connects AC networks of varying voltages.