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What factors determine proper generator sizing?

Power generation is needed in an endless variety of locations and environments, with each installation having different factors affecting generator requirements. Incorrect generator sizing can be disastrous in any power generation project if particular installation factors are not properly taken into account.

Many OEM’s and end users are posed with the task of sourcing the most efficient and cost-effective generator that meets all applicable customer and project certifications and requirements.  Without knowing and understanding all necessary installation details and factors that go into proper generator sizing, this can be a very difficult task.

The operating environment of a generator set is one of the biggest factors that affects the size of machine needed for a given kVA load.  Environments can range from sub-zero to 60° C ambient temperatures and can include harsh conditions and contaminated cooling media, which impact enclosure selection.  Extremely harsh, contaminated operating environments can require a cooling enclosure that will almost double the size of generator needed to produce the same kVA output as a unit in a controlled environment.  Operating altitude is also very important to consider.  As elevation increases, air density and cooling capacity decrease, and therefore a larger cooling system is needed.

In addition to environmental factors, there are many electrical considerations that affect generator sizing as well.  For example, for a given kW required, a lower power factor drives the need for a larger generator.  Also, frequency and RPM (determined by the prime mover) will directly impact generator size.  The physical size of the machine required for the same kVA output can double if speed is cut in half, due to the need for an increase in number of poles.

Additionally, insulation class (temperature rise allowance) is a big component in generator selection. While lower temperature allowance can greatly increase the overall lifetime of your generator, a larger unit will be needed to produce the same kVA as a unit with higher temperature allowance.

As important as any of the topics above when it comes to generator sizing is non-ideal loading conditions.  Possible high harmonic and unbalanced loading levels require a larger unit to handle the maximum level of unbalance that the machine may be exposed to.  This concept applies to motor starting and block loading capabilities too.  A bigger machine is required to minimize the voltage dip caused by motor starting.

The topics discussed above are a brief introduction to all concepts and factors that play an important role in generator sizing.  Our upcoming webinar “Properly Sizing Your Generator” will examine and explain these topics and more in greater detail to ensure that you are selecting the right generator for your next project.

Nidec – Kato Engineering/Leroy-Somer branded low, medium, and high voltage generators are the reliable choice for genset packagers and power producers worldwide.  Our proven engineering expertise and state-of-the-art manufacturing processes ensure that our generators will out-perform and out-last in any environment.  We offer both standard and custom product design solutions to meet any power generation project needs.

Register now for our “Properly Sizing Your Generator” Webinar to learn more detailed information on selecting the optimal generator for your next project.

Learn More at Upcoming Webinar

Understanding all mechanical and electrical considerations that factor into properly sizing a generator is key to ensure trouble-free and efficient generator operation. Register for this webinar here to make sure your future power generation projects are properly planned.

Here are the details of our Webinar:

Date: Wednesday, November 14

Time:  3PM London/10AM New York

Presenter: Jacob Jewison

Job title: Electrical Engineer








Join Nidec – Kato Engineering & Leroy-Somer Live Webinar “Properly Sizing Your Generator” on 14 November at 3PM London/10AM New York

Register Here!