What engine ratings should i choose for my generating set application?

Selecting an engine should be a process undertaken in conjunction with selecting the ac generator and both these important components need to be jointly chosen as part of a structured plan for the project. It should start by fully understanding of the use to which this generating set is to be specifically applied and the environmental conditions which will be encountered at the proposed site of installation. Or considering a specification and capability requirement which covers a range of applications for the equipment packages to be described as performance capability within a technical/sales brochure.

There are various Engineering Standards which offer helpful advice regarding the capability and performance expectations for engines, with some extending through to cover technical details for the ac generator, and providing details of generating set industry related performance and associated classification for a complete generating set.

Engineering standards specifically addressing engine capability and specifications are:

  • DIN ISO 3046
  • SAE J 1995 / J 1349
  • BS ISO 8528 part 2

Engineering standards specifically addressing an ac generator’s capability and specifications are:

  • IEC 34 (which has some 30 parts)
  • BS ISO 8528 part 3

An engineering standard, with associated parts specifically addressing generating set equipment capability and specifications is: BS ISO 8528

  • part 1. Applications, Ratings & Performance
  • part 2. Engines
  • part 3. ac Generators
  • part 4. Controlgear and switchgear
  • part 5. Generating sets
  • part 6. Test methods
  • part 7. Technical declarations
  • part 8. Requirements and tests for low power generating sets
  • part 9. Measurements and evaluation of mechanical vibrations
  • part 10. Measurements of airborne noise
  • Part 12: Emergency power supply to safety services
  • Part 13 Safety

For engines, it is important to determine the kind of power output rating that will be required for the proposed application and its related Duty. The ‘kinds’ are categorised as:

  • Continuous (COP)
  • Prime (PRP)
  • Limited Time (LTP), which covers Stand-By.

The proposed generating set’s application will determine the kind of engine power rating required, and this in turn will clarify the ac generator’s rating which may be Industrial or Marine and then a series of Continuous or Standby thermal classifications which will then set the type of generator required for the proposed duty.

BS ISO 8528 part 1 provides a good starting point for becoming familiar with generating set terms and performance categories.