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Key Factors to Consider When Purchasing a Diesel Generator

  • October 15, 2019

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Key Factors to Consider When Purchasing a Diesel Generator

The backbone of industrial estates, construction sites, outdoor events, residential complexes; a generator is essential irrespective of whether the location is grid-connected or not. While most project sites with access to the grid would keep a generator as standby, remote locations and outdoor events where grid lines are non-existence, a generator is the only source of electricity. Considering the importance of generators proper research and knowledge must be applied before purchasing one. Most medium and large enterprises opt for a diesel generator for their power requirements. Given below are some key factors to keep in mind before investing in a diesel generator.

Load Factor

It is rather simple to calculate the total load required by adding up the starting load requirements of the different types of equipment that will be running on the power generated. The inrush currents for starting transformers and motors can be as high as six times the full load current. Electric motors today are efficient and their stating load can be double that amount. Thus, you end up with a generator that is oversized for the running load required. Another key factor while determining the size of the generator is the harmonics caused due to the sequential or variable starting of multiple motors. If the generator is not sized according to the load requirement, you could end up with frequency and voltage drops when starting transformers or motors.

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Fortunately, many current day generators are equipped to handle this added excitation system required. You could get the advice of an expert to learn more about the different capabilities of the current range of generators. To provide a generator with up to three times more than their nominal current, two options are offered in the form of auxiliary winding or a permanent magnet. They provide extra current for around ten seconds to cover the required inrush peak. An even more advanced option is the D-AVR (digital automatic voltage regulator) that allows you to downsize your generator load requirement. Useful for magnetizing step-up transformers where medium voltage is required, the ‘Close Before Excitation’ system in generators is another option to look at.

Thus, it is no longer required to purchase a generator with a high load factor just to cope with the initial surge when starting motors and transformers.

Autonomy and Fuel Efficiency

Fuel cost is spiraling upwards and will continue to do so in the future. Thankfully, most generators today are designed e to be energy efficient and consume far less fuel than their predecessors. But it still makes sense to ask about and compare the fuel consumption of different generators before making your purchase. A factor to consider while looking at fuel consumption is modularity. Three 325 kVA generators would consume around 1.558 liters of fuel as compared to 1.677 liters consumed by a 1 MVA generator doing the same job.

Power Management and Control System

Generators today offer a host of control system options such as warning display, remote start and stop, low fuel indicator and a range of data for analysis. This ensures that the generators are used to their maximum efficiency and trouble-free. Ideally suited for rental applications, many generators feature Power Management Systems. This allows the operator to optimize the load demand and fuel consumption according to the increase or decrease in the load required, thus ensuring that there is no engine damage due to running with low load levels.

Modular Capability

While you may have planned and purchased a generator for your requirement as of today, what would you do when your requirement increases? This is where you need to check if the generator can run in parallel with other generators to form a modular unit. Generators with this capability normally require around ten minutes to pair them up with each other. However, it is best to ask before you invest. The modular capability allows the operator to run all or a few generators according to the load requirements. Another advantage of modular set-up is when one unit fails for some reason the others can be ramped up to take the extra load.


Size does play an important role in selecting a generator. Whether the generator is to be installed permanently at a location or moved from one location to another, the size of the generator has to be worked out. If installed at one location it has to fit into the space allocated. For generators that need to be loaded on to a truck and moved around, the size should match the vehicle capacity.

Points to Remember

Calculate the load factor and stay on the conservative side. Think modular, even when looking at smaller loads. Get expert advice and ask questions regarding the generator, its maintenance and after-sales service provided.