Despite the growing use of generator sets (gensets) to mitigate power disruptions, there is still confusion about how to choose the appropriate genset based on specific operational demands, notes WEG Africa senior manager Gensets Craig Bouwer.

“Understanding the specific application of the genset is crucial for the right selection, and the first step is knowing that genset applications are broadly categorised into standby, prime and continuous, each with distinct operational requirements,” he says.

Standby gensets are usually used only for emergency situations. These units have a limit on operational hours a year and a specific load factor. In South Africa, the frequency of loadshedding means that most gensets are not used solely for standby purposes, and prime and continuous applications are more commonly used.

Prime gensets can run unlimited hours annually with variable loads, maintaining an average load factor below their maximum rating. Continuous gensets also operate unlimited hours, but with a constant and predetermined load.

WEG Africa engineering manager Damian Schutte explains that understanding the difference between prime and continuous ratings is also critical. The load factor is a key differentiator and not the unlimited time requirement, with prime applications having variable loads and continuous ones having fixed loads.

Schutte uses a vehicle analogy to illustrate the differences: a continuous genset is like a car on cruise control operating at a steady speed within its capacity on a long-distance trip, while a prime genset is akin to a vehicle driving in the city. Standby can be perceived as racing between traffic lights.

The choice of genset rating impacts its expected lifespan and maintenance needs. For example, continuous power may be required in mines during loadshedding to supplement limited grid power, while industrial applications, such as workshops with variable loads, would need a prime-rated genset.

Bouwer notes that standby power remains vital in essential service sectors for health and safety reasons, especially in environments such as mines, hospitals and data centres.

As an original equipment manufacturer, WEG Africa explains that it uses these categories to guide customers to make the correct genset choices, aiming to match specific needs and expected service life. The company cautions against oversimplifying the selection process by just matching the total load with a genset's nameplate rating, as this can lead to premature failure and additional costs.