Questions and Answers

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How to choose a generator set and which generator set to buy?

Some of the basic questions that need to be answered when choosing a generator set
Purpose (application) for which the generator set will be used?
Required type and power of the generator set?
Needed reliability?
Method and place of installation of the generator set?
Generator set price (budget)?

First you need to choose which type and power of the generator set you need:

  • Single-phase (230 V, 50 Hz): to supply only single-phase consumers up to 20 kVA
  • Three-phase (400 V / 230 V, 50 Hz): for powering three-phase and single-phase consumers from 3 kVA to 20 kVA
  • Portable petrol or diesel - for power up to 20 kVA
  • Stationary - from 10 kVA to 2000 kVA
  • Open type of generator set - intended for indoor installation
  • Container type of generator set (canopy) - designed for outdoor installation and can be installed inside the building (protection from atmospheric conditions and noise protection)

Required generator set power

The selection of the power of the generator set is a complex process and is based on the calculation of consumer power, type of consumer, the way of load step sequencing all consumers to be supplied from the generator set and the calculation of voltage drops caused by consumers during startup.

If there is no electric motor drive, the power of the generator set is obtained by adding all the apparent power of the consumer (kVA) and adding a reserve of at least 10% and choosing the first larger type of generator set.
If there is an electric motor drive, the condition is that all electric motors over 3 kW are started via a soft starter or a star triangle or frequency regulator. Then the power of the generator set is obtained by adding all the apparent power of the consumer and adding twice the value of the apparent power of the largest electric motor and choosing the first larger standard generator set.

Required reliability

Depending on the application for which it will be used, the required reliability of the generator set is chosen. If consumers are very important and high reliability of the generator set is required, the following elements must be taken into account when choosing the generator set:

  • ENGINE - The engine of a renowned European manufacturer with secured service and spare parts is selected: PERKINS, FTP IVECO, VOLVO…
  • GENERATOR - The renowned European manufacturer STANFORD, MARELLI, MECC ALTE, LINZ, SINCRO is chosen…)
  • MICROPROCESSOR CONTROLLER - To control the operation of high-reliability generator sets, controllers from manufacturers that can be found in stock and in our market are chosen (COM AP, DSE, DATAKOM…)
  • ATS (Automatic Transfer Switch) - Cabinet for switching consumers network / generator set - Components of renowned European manufacturers (ABB, SCHRACK, SCHNEIDER, NOARK) available in our market are chosen
  • SERVICING - Trained and equipped servicing department, for quick response, available 24 hours a day, seven days a week, is one of the key factors in choosing a generator set.

Additional elements when choosing a generator set:

  • Redundant (special, independent) generator set control system - With independent sensors, used in case of failure of the basic one
  • Cabinet BYPASS - Independent cabinet through which power can be transferred in case of ATS cabinet failure
  • SCADA - Remote monitoring and control of generator set operation
  • Method and place of installation of the generator set - In order for the generator set to be used smoothly, it must be installed according to the required conditions:
  • Room where the generator set and equipment are located: (room dimensions)
  • Room ventilation - Calculation of the required amount of air and selection of the most suitable way to ventilate the room
  • Preparation of generator set foundations - Calculation and drawing of foundations based on chosen generator set
  • Fuel delivery method
  • Exhaust system construction
  • Generator set price

Nowadays, the time of economic crisis, the price of aggregates, is one of the most important elements in his choice. It is, undoubtedly, a factor based on when to choose the generator set, but first you need to meet all the technical requirements of the generator set, take into account the purpose for which it will be used and then based on the selected product group, choose the generator set whose price is best.

How to understand the power of the generator set?

In order to fully understand the concept of power in electric generators, it is necessary to understand the following three concepts, apparent power C expressed in KVA, active power P expressed in kW and reactive power Q expressed in kVAr.

Where, therefore, P is, active power, power that performs useful work. It represents most of the apparent power and is spent on supplying active consumers, purely reactive loads (consumers).

Q is reactive power, power that is used to cover various losses within the unit, but also to supply energy to reactive consumers (magnetization of magnetic circuits of individual devices, fluorescent lighting, asynchronous motors, voltage regulation on transformers, etc.).

S is the apparent power, so to speak, the total power generated by our generator. It has both active and reactive components, thus covering both active and reactive reactive energy consumption. The power factor, cos φ, represents the ratio of active power and apparent power, cosφ = P / S.

Analogous to this explanation, we will observe a mug of beer from the picture below. When we order a mug of beer at the bar, we get the following, a mug with a volume of 0.5 l. This volume is analogous to the power S, we asked for 0.5 l and we got it. Inside the mug there is a liquid part, a part that serves for our enjoyment and refreshment, as well as for our consumers. This is the part of energy that we as consumers directly feel and enjoy. Finally, to the top of the mug, there is foam, it is there to fill the mug completely, in the case of a generator it is Q, it covers losses due to electricity transmission, magnetizes transformers to maintain a constant voltage. So, energy that we cannot directly feel, but it certainly exists and has its purpose, fulfilling our electrical needs, just like the foam that fills a mug.


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