What is a generator set and how to calculate its power?

Generator sets are machines used to respond to the electrical needs of an installation, either as a main source or as an auxiliary source. The most common, however, is that the generator sets are used to supply the possible energy deficiencies that may exist in certain installations.

What is a generator set and how to calculate its power?

In the case of a photovoltaic solar installation, this can be very useful when the batteries are not enough and when the installation is isolated. That is, it is not connected to the general electrical network. In this article we explain what a generator set is and what is the function of a generator set for solar installation. We also answer how calculate the power of a generator set and what is its maintenance.

What is a generator set?

Generator sets are machines that move an electric generator thanks to the function of an internal combustion engine. These take advantage of heat energy to convert it into mechanical energy and, later, into electrical energy. The generator sets are used, in general, when there is a deficit in the generation of electrical energy in a specific place. For example, to prevent power outages in a hospital or in a factory where the machinery cannot be stopped. We can also find small generator sets for solar installations (solar energy generator set). In the latter case, the device is used to supplement the energy generated through photovoltaic solar panels in isolated installations.

Components of a generator set

As we explained above, generator sets —whether they are solar-powered generator sets or for any other use— work with an electric generator that is activated by an internal combustion engine, usually gasoline. The generator set is made up of the following parts:

• Motor: It is the main component of the generator sets. This is used to generate the mechanical energy in order for the alternator to start working. The engines of the generator sets can be gasoline or diesel, depending on the model.
• Alternator: The alternator is the component that is responsible for transforming the mechanical energy produced by the engine into electricity. The choice of one alternator or another will depend on the use that the generator set will have. That is, if it works as a support or as a main use.
• Bodywork: It is the sheet or cover that protects the generator set. This has an anti-corrosive treatment and ensures that the air flow is optimal inside, preventing overheating.
• Load Transfer Frame: This piece of equipment is used to alternate between the main and auxiliary power sources in the event that the former fails, thus ensuring a constant supply. In the case of a solar generator set, the load transfer frame would act between the photovoltaic solar circuit battery and the generator set.
• bench: It is used to avoid vibrations of the generating set when it is in operation.
• Control Panel: Varies depending on the model, since not all include it. The control panel is used to monitor the generator sets by controlling their operation and to protect them against possible malfunctions.
• Others: Other parts that we can find in the generator sets are the cooling systems, the silencers and exhaust systems, the automatic output switch…

Keep in mind, likewise, that a generator set can be complemented with other elements. For example, with the batteries in the case of solar power generator sets, which will be prioritized to be used before the generator is activated. When the generator set is located in a place far away from the operator, or works 24 hours a day, it is necessary to install a mechanism that restores the consumed consumable. That is known as the transfer pump.

How to calculate the power of a generator set

To answer how to calculate the power of a generator set, it is important to first answer some questions. These will help us choose one model or another and know which one best suits our needs. So, before buying a generator set, ask yourself the following:

• What are you going to connect in your generator set?
• How do you need to connect the devices to your generator set?
• How often will you use the generator set?

Once you know this data, the next thing you should take into account is the active power. Remember that the power you really need is not only what is generated and can be absorbed by the device, but also what is used and lost in the circuit. Therefore, it is important to know what its value is. To do this, solve the following formula: Active power (kW) = Reactive power (kVA) * Power factor (pf). In the case of the power factor, use the value of 0.8 to complement the equations, since it is the most common in terms of energy use.

There are two more things you need to keep in mind, first of all. This is the calculation of constant power and the power you need taking into account the boot type. The first of the cases refers to the constant power that the equipment will have without there being a starting peak —that is, with the devices and equipment already in operation—. As for the type of start, the opposite happens and this depends on whether it is light (the value of the constant power is multiplied by x2 or x3), if it is medium (the value of the constant power is multiplied by x3 or x4) or if it is burdensome (the value of the constant power is multiplied by x4 or x5).

Formula to calculate the power of a generator set

With everything explained, we can now proceed to calculate the power of a generator set. You must apply the following formula: kVA = kW / PDF. To the result, remember to apply a safety margin with an increase of 10% or 20% to prevent the group from working at 100% at all times and to be able to connect another device if necessary.

Things to keep in mind when calculating the power of a generator set

Keep in mind the following when you go to perform the calculation:

• Generator sets are universally identified by the power in kVA.
• Add the power of all the devices you are going to connect.
• Consider the starting peak and contemplate the different options that are available to you.
• When you have the kW you need, divide it by the power factor (PDF) to get the kVA (real or apparent power).
• Take into account the margin of error and multiply the result by 10% or 20%.

How is the maintenance of a generator set

Without going into many details, we are going to explain in a concrete and summarized way what are the steps that you must carry out to maintain a generator set. Please note the following:

• The maintenance period It depends on the use it will have. If it is supportive, you will need to review it approximately every 3 months; while, if it is continuous, a review may be necessary every 250 or 500 hours. Check the manufacturer’s specifications.
• Start the generator once a week.
• Check the oil levels.
• Change oil and filters when necessary.
• Check the auxiliary element belts and adjust them after the engine has been running. Adjust them when they are still warm, but with the system turned off.
• Check the cooling system and check that the coolant levels are at the optimum values.
• check the alternator. In this case you will have to check the condition of the winders, maintain and replace the bearings, as well as the batteries or refilling and check the charge of the batteries.