Choosing a generator shouldn’t be a difficult decision, however choosing which generator is a lot more complex. Deciding if you need a single or three phase generator is the first step ensuring you have the power unit which is going to meet your energy needs and suitable backup power should you experience a power outage.

Before explaining the difference in single or 3 phase diesel generators, it is important to understand alternating current (AC). AC is a form of electricity were the flow of power is continuously changing direction. It is this type of current which is delivered into our homes and businesses.

What is the difference between single phase and 3-phase?

In a single-phase system, the power is supplied through two wires, phase and neutral. This means that the power delivery is constantly changing and is maximum at two points in a cycle. This is perfect for many applications such as heating and lighting but is less suitable for larger motor loads.

In a 3-phase system, the load is shared across three phase wires. This can be considered as three equal but independent single phase supplies. These three supplies have a time or phase difference of 120º. The most common 3 phase connection is called the star connection with one end of each of the three phases being connected at a common star (or neutral) point. By doing this, the three phase voltages, and hence power, peak at different times during a complete cycle. The sum of the three phases at any instant is always a constant value meaning that power is supplied constantly. This is much more suitable for large motor loads.

When Should I Use A Single Phase Or 3 Phase Power Supply?

Selecting a single phase or three phase system all depends on the power needs of a specific application. If you imagine one person carrying a load up a mountain, there will come a time that it will become too tough for one person. Now image three people sharing that load at different stages splitting the work by a third, they can carry it further and not get tired. It’s similar to single and 3 phase electricity, the following are examples of typical of items requiring single or 3 phase generators.

Single Phase

• Single home

• Power tools

• Site Lighting

• Domestic applications e.g. Houses small electric motors (under4kw)

3 Phase

• Large complex

• Electric Motor above 4kw

• Industrial/Commercial applications

Benefits and Uses of a Single Phase AC Power Supply

Single phase power supply units have a broad array of applications. Units that have a limited power need up to 3000 watts typically make the most efficient use of a single phase AC power supply. Generally, benefits of selecting a single phase system include:

• Broad array of application uses

• Most economic AC power supply for up to 3000 watts

• Fewer design costs

• Less complex designs

Benefits and Uses of a Three Phase AC Power Supply

Typical applications for 3 phase systems include data centres, mobile towers, power grids, aviation, and anything with a load greater than 3000 watts. Three phase power supplies offer a superior capacity for higher load systems. Some of the benefits include:

• Reduction of copper utilisation

• Ability to run higher power loads

• Constant power delivery to motor loads

Regardless of whether you need a single phase or 3 phase generator you can be guaranteed that AJ Power can provide a diesel generator to meet your project needs in addition you will have the support of our experienced team.

All our gensets are designed and manufactured at our HQ in the UK. We offer our customer a choice of engine and alternator which ensures you have the best option for your power needs.

For further information on which best suits your needs contact are sales team on or visit our website at

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