Rating Definitions

A Generator set (genset) consists of an engine and a generator. However, it is best to consider the engine and generator as a system. Individually, each has unique characteristics, but together these qualities have a significant impact on the performance and sizing of the genset system.

Capabilities of both engine and generator are considered individually and collectively when selecting generator sets. Engines produce brake horse power (or kilowatts) while controlling speed or frequency. Generators influence engine behaviour, but are primarily responsible for changing engine power into kilovolt-ampere (kVA) and electrical kilowatts (kW). They also must satisfy high “magnetizing current” draws (kVAR), or transient conditions from electrical equipment.

Normally, a generator ser is furnished with generator which macthes the engine output capability. Engines are sized according to the actual power in kW required to meet the needs of the facility. The generator, on the other hand, must be capable of handling the maximum apparent power which is measured in kVA. The actual power can be identified in several ways. It can be calculated by adding the nameplate ratings of the equipment to be powered by generator. If this is done, the efficiencies of the equipment must also be considered. The actual power can be determined by performing a load analysis on the facility. This involves making a survey of the power requirements over a period of time.

Generator Set Rating1. Standby rating2. Prime rating3. Continuous ratingStand by rating is used for emergency power (on emergency systems) for duration of normal power interruption. Average power output is about 70 % of the standby power rating with no sustained overload capability is available. Some diesel such as caterpillar has typical operation is 50 hours per year with maximum expected usage of 200 hours per year.

This rating are generally installed as required for public safety and typically intended to provide power and lighting for short periods of time one of three possibilities situation : to permit save evacuation o buildings, for life support and critical equipment for vulnerable people, or for critical communications systems and facilities.

Prime rating is used to supply power output with varying load for unlimited time which has average power output is 70% of the prime power rating. Typical peak demand of 100% of prime-rated ekW with 10% of overload capability for emergency use for maximum of 1 hour in 12. Overload operation cannot exceed 25 hours per year. Prime power in accordance with ISO8528. Fuel stop power in accordance with ISO3046.

Has complex contruction fuel , anti-vibaration, station, exhaust cooler.

Widely use as power supply for a remote mining or construction site, power supplier for energizing electrical motor on crane or similar equipment.

Continous rating is used for suppliying power continously to an constant load up to the full output rating for unlimited hours. No sustained overload capability is available for this rating. Continous in accordance with ISO8528. Fuel stop power in accordance with ISO3046.

Typical ly used for supplying continous unvarying load, or paralleled with the mains and continously feeding power at the maximum permissible level 8.760 hours per year. This also applies to sets used for peak a having/grid support even though this may occur for say 200 hours per year.

As an example if in a particular set the Standby rating were 1000 kW, then a Prime Power rating might be 850 kW, and continues rating 800 kW. However these ratings vary to manufacturer and should be taken from the manufacturer’s data sheet.Sizing

Most of generator set combines Diesel engine which is connected to the generator which is used for wide purpose for homes, small shops & offices, factories or for generate electrical power in power plant or to energize electric motor in crane. Few, for small purpose use gasoline such as for homes.

For the reason, we must have good understanding how to choose generator set to meet our requirements. First of all is sizing.

Sizing of generators is critical to avoid low-load or a shortage of power and is complicated by modern electronics, especially non linear loads.