The key success once selecting a rating is to understand the application where the generator will be used. Including the following major factors.
• Average load factor
• Maximum required load needed
• Identifying the running usage required per year
• Do you need multiple units running at the same time (Synchronization) option, or single unit
RATINGS DEFINED
STPEC defines ratings as per ISO-8528, the basic generator set ratings are: Standby Power, Prime Power, and Continuous Power.
Standby
In Standby Power application, the generator set can provide100% of its rated nameplate power. However, the average load factor of a Standby rated generator set should be not exceed 70% of its rated power with varying loads per year. A Standby generator set can run for a maximum of 500 hours per year and other cases 200 hours per year. No overload is available with a Standby rating.
Prime
In Prime Power application, the generator set can provide100% of its name plate rating with varying load for an unlimited number of hours per year. However, the average load factor should not exceed 70% of the Prime rating per year. Ten percent overload is allowed for a maximum of 1 hour in 12, and for no more than 25 hours per year.
Continuous
In Continuous Power application, the generator set can provide power with constant load for an unlimited number of hours per year. The average power output of the generator set is 70 -100% of the rating. No overload allowed.
Conclusion
Regardless of the application, generator set ratings help ensure that end-users are protected for the type of application being used. Choosing the right rating will lead to optimum combination of installed cost and long-term operation cost.
