Generators – What Are They And How Do They Work?

We all know that generators are useful appliances that can supply electrical power during a power outage, and prevent the cutoff of daily activities or the disruption of various day-to-day business operations. Generators are available in a wide array of different electrical and physical configurations for use in different applications. Throughout this blog, we’re going to look at just how a generator operates as a secondary electrical source in both residential and industrial applications and some of the main components of a generator.

An electric generator is a device that converts mechanical energy obtained from an external source into electrical energy as the output. It’s very important to understand that a generator doesn’t actually create electrical energy; it uses the mechanical energy to force the movement of electric charges present in the wire through an external electric circuit.

The flow of the electric charge mentioned above helps to establish the output of the electric current supplied by the generator itself. If you’d like to understand it properly, you can compare the generator to a water pump, which causes the flow of water but doesn’t create the water flowing through it.

’Modern’ generators work on the principle of electromagnetic induction, which was first discovered by Michael Faraday in 1831. Faraday discovered that the flow of electrical charges could occur when moving an electrical conductor, such as a wire that contains the charges, in a magnetic field. Once the movement occurred, it created a voltage difference between the two separate ends of wire, which caused the electric charges to flow, generating electric current

Generators – The Main Components

The main components of a generator can be classified as follows:

  1. Engine – The engine is the main source of the input mechanical energy to the generator. The size of the engine is proportional to the maximum power output that the generator can supply.
  2. Alternator – Sometimes known as the ’genhead’, the alternator is part of the generator that produces the electrical output from the mechanical input supplied by the engine.
  3. Fuel System – The fuel tank of a generator usually has a big enough capacity to keep the generator operational for 6-8 hours on average. If you have a smaller generator, the fuel tank is a part of the generator’s skid base or is even mounted on top of the generator frame.
  4. Voltage Regulator – This component regulates the output voltage of the generator.
  5. Cooling and Exhaust Systems – Continuous usage of a generator can cause it’s components to get heated up. It’s vital that your generator has a cooling and ventilation system, to withdraw the heat that is produced in the process.
  6. Lubrication System – Lubrication is required to ensure durability and the smooth operation for a long period of time. It is lubricated by oil stored in a pump.
  7. Battery Charger – The start function of a generator is battery-operated; the battery charger keeps the generator battery charged by supplying it with a precise ‘float’ voltage.
  8. Control Panel – The control panel is the user interface of the generator and contains provisions for the various electrical outlets and controls.
  9. Main Frame/Assembly – Both portable and stationary generators have customised housings that provide a structural base support. The main frame also allows for the generator to be earthed, for safety reasons.

"When looking on Google for electric generator hire near me I came across Bellwood. Spot on service used them for years ever since. Always on hand to help!"

- James Kirkup

Over the years, generators have proved themselves to be worthy servants for many home and business owners around the globe, providing a valuable backup power source for properties that might have otherwise been without power if it weren’t for them.

As with anything, it’s easy to take electricity for granted; after all, it’s around most of us every day. For all you might understand what electricity is and how it works, that doesn’t make it any easier to cope with a situation when there may be no power due to damaged infrastructure or a failure with the power grid. Having a generator doesn’t mean just paying for it and hoping it works when the power goes down. If you are truly considering going down the route of buying a new generator, it’s a wise idea to learn how it works and understand the way it fills the void of power, during a power cut or when there is no power nearby.

Below, we look at how generators work, and the different things needed to make them function effectively.

How Do I Determine the Right Size Generator for My Needs?

One of the most critical aspects of installing a backup or prime generator is ensuring it is adequately sized. At Bellwood Rewinds, we understand the importance of getting the size suitable for your generator requirements. An undersized generator will not be able to provide sufficient power, leading to potential issues such as selective powering of electrical components or even generator failure during operation. This can result in damage to connected devices and premature generator failure.

Some may consider installing a smaller standby generator, assuming it won’t run continuously. However, it is essential to recognise that when a standby generator is needed, it must have the capacity to power the entire facility. 

Therefore, regardless of the operational schedule, the generator must be sized appropriately to meet the power demands.

While opting for a slightly larger generator rather than an undersized one is generally advisable, large generators also present challenges. Installing a generator that provides significantly more power than necessary can lead to the wastage of resources. This includes overspending on the generator, higher fuel and consumable costs, and potential risks of damaging connected devices.

Generators come in various power capacities, ranging from 5 kW to 50 kW in the residential market and from 50 kW to over 3 Megawatts in the commercial and industrial sectors. With such a wide range of options, determining the right generator size can be complex. To ensure accurate sizing, we recommend consulting with a certified electrician who can assess your specific power needs, evaluate your electrical system capacity, and advise on any necessary upgrades and optimal installation methods.

However, you can also get a preliminary idea of your power requirements by following these steps:

  1. Create a comprehensive list of all the electrical components that need to be powered by the generator.
  2. Note down the starting and running wattage of each item. This information can typically be found on the device’s identification plate or in the owner’s manual.
  3. Calculate the total power requirements in kVA or kW. Some devices may specify power requirements in amps, which must be converted to kW or kVA. You can use online power calculators to assist with these conversions.

Once you have determined your facility’s total power requirements, you can select a generator that meets your needs. Consider exploring used and surplus generators as cost-effective options that still provide reliable performance. Used generators, when properly maintained, can offer many years of service. Reputable generator suppliers like Bellwood Rewinds ensure thorough checks, review maintenance records, and may even perform necessary repairs before selling a used generator. Surplus generators are another viable choice, often with minimal or no running hours. These machines offer similar benefits to used generators but without extensive previous usage.

At Bellwood Rewinds, we are committed to helping our customers find the right-sized generator for their specific requirements. By working closely with our clients and offering expert advice, we ensure that the chosen generator can provide reliable power when needed.

How does a Generator Create Energy to Produce Electricity?

Whether you opt for a standby generator for backup power, you’re preparing for an expected/unknown disaster or you need a generator to help you power tools and equipment on a construction site away from a nearby power source, most generators create energy in the same or similar ways. At the same time, most generators will carry the same challenges, so it’s worthwhile looking into how they work.


The burning of fuel makes it possible to produce mechanical energy that runs an engine. This is what gives your generator the energy needed to supply you with a backup power source.

Different types of generators can be purchased that use different fuel types, including diesel, petrol and gas. You’ll find that a lot of larger, standby generators work using diesel, whereas the smaller generators will use petrol or gas.

The Engine

The generator engine will burn the fuel to produce the mechanical energy required. Similar to that of cars and other engines, the engine of your generator also requires coolant and oil to operate effectively, with regular maintenance required to ensure your generator maintains performance levels. Following the manufacturer’s recommendations, both the oil and the coolant should be changed regularly. Most small, portable generators will work using an air-cooling system, while larger, standby generators will require liquid coolant to prevent the engine from overheating.

The size of the engine will depend completely on what you need it for, taking into consideration how much electricity you need to cover. If you aren’t sure what size generator you need, try using a wattage calculator to determine how much electricity usage your equipment, appliances etc. will equate to.


As your engine burns fuel, the mechanical energy it creates is transmitted to the alternator, the same as it does in cars and other vehicles. A generator alternator has several components to it. A rotor inside rotates to create a magnetic field in the slator, which is made of an iron core, wrapped in metal coils and doesn’t move. The role of the slator is to conduct electricity, while mechanical energy is used to create electricity inside the alternator casing as the rotor spins.

Voltage Regulators

To control the electricity, a voltage regulator is required to help make sure the generator still has enough electricity to continue working when electricity is pulled from an external source. The first lot of energy that is used by a generator, when it is turned on, is to make itself work. After this, it will build up electricity so that power can be output to other areas. Once this energy starts getting used, the voltage regulator will interact with the alternator so that it creates more current, until the point where it is at capacity.

The Exhaust System

Like any other engine that burns fuel, an exhaust system is required to release the gases that are created in the engine. The exhaust system should release the gases out into the open air, rather than into a confined space where it could become trapped. Gases released by burning fuel can be potentially dangerous if they are inhaled, so caution should be exercised when using/installing a generator of any kind.

Most generators will vary slightly in one way or another, with subtle differences between one model and the next. As this is just a basic overview of how most generators work, you should still take the time to learn how yours works best if you have already bought one or plan to purchase one soon.

Frequently Asked Questions

A generator converts mechanical energy into electrical energy. It does this through a process called electromagnetic induction. When an electrical conductor, such as a wire, moves within a magnetic field, it creates a voltage difference that causes electric charges to flow, generating an electric current.

The engine in a generator serves as the primary source of input mechanical energy. It is responsible for burning fuel, such as diesel, petrol, or gas, to produce the rotational motion required to turn the generator’s rotor. The size of the engine determines the maximum power output the generator can provide.

The alternator, also known as the “genhead,” is the generator component that converts the mechanical energy from the engine into electrical energy. It consists of a rotor and a stator. A magnetic field is created as the rotor spins within the stator, which induces a voltage in the stator windings, generating electricity.

The voltage regulator plays a crucial role in maintaining a stable output voltage from the generator. It regulates the electrical output by controlling the excitation current supplied to the alternator’s rotor. This ensures the generator delivers a consistent voltage level, protecting connected devices from potential voltage fluctuations.

Continuous usage of a generator can cause its components to heat up. To prevent overheating, generators are equipped with cooling and exhaust systems. These systems help dissipate the heat generated during operation. They may include cooling fans, air vents, and exhaust pipes that facilitate the flow of air and exhaust gases to maintain safe operating temperatures.

Contact Bellwood Rewinds Today

For further technical support, please contact Bellwood Rewinds if you need advice on how generators work/how best to set up a recently purchased generator.