Do you know the difference between kilowatt (kW), kilovolt-ampere (kVA), and power factor (PF) for diesel generator sets?

    Diesel generator sets have been used in all walks of life, and are the first choice for power equipment to provide backup power in the event of a power outage or for daily electricity use in enterprises. Diesel generator sets are also often used to provide power in remote areas or field operations. Although many users use Diesel generator sets but confused about the difference between kilowatts, kVA, and power factor for diesel generator sets.

• Kilowatts (kW) are used to measure the actual power provided by the generator, which is used directly by appliances and equipment in the building.
• Kilovolt-ampere (kVA) measures apparent power. This includes active power (kW), but also reactive power (kVAR) consumed by equipment such as motors and transformers. Reactive power is not dissipated but circulates between the source and the load.
• Power factor is the ratio of active power to apparent power. If the building consumes 900kW and 1000kVA, the power factor is 0.90 or 90%.

     Diesel generator nameplates have kW, kVA, and PF ratings. To ensure that you can choose the most suitable diesel generator set for you, the best advice is to have the size of the set determined by a professional electrical engineer.

    The generator's maximum kilowatt output is determined by the diesel engine that drives it. For example, consider a generator driven by a 1000 hp diesel engine with 95% efficiency: 1000 hp is equivalent to 745.7 kW, which is the shaft power supplied to the generator. The efficiency is 95% and the maximum output power is 708.4kW.

    The maximum kVA depends on the rated voltage and current of the generator. There are two ways to overload the generator set:

• If the load connected to the generator exceeds the rated kilowatt, it will overload the engine.
• If the load exceeds the rated kVA, it will overload the generator windings.

    This is very important because the generator can be overloaded in kVA even if the load kilowatts is below the rated value.

•  If the building consumes 1000kW and 1100kVA, the power factor will increase to 91%, but will not exceed the generator set capacity.
•  If the generator runs at 1100kW and 1250kVA, the power factor only increases to 88%, but the diesel engine is overloaded.

    Diesel generators can also be overloaded in kVA only. If the equipment is running at 950kW and 1300kVA (73% PF), the windings will be overloaded even if the diesel engine is not overloaded.

    All in all, diesel generators can exceed their rated power factor with no problem, as long as the kW and kVA remain below their rated values. Going below rated PF is not recommended as the generator operates less efficiently. Finally, exceeding the kW rating or the kVA rating can damage the device.