A generator set is an autonomous power generation system consisting of an internal combustion engine coupled to an alternator. Correct specification is critical to ensure electrical stability, protection of sensitive loads and operational continuity at construction sites, industries and events.
1. Nominal Power: kVA vs kW
Generator sets are usually specified in kVA (kilovolt-ampere), which is apparent power. However, the active power available in kW depends on power factor (PF).
Basic formula:
kW = kVA × PF
Example: A 100 kVA generator at 0.8 PF delivers 80 kW of active power.
2. Operating Regimes
- Standby: emergency operation for limited time.
- Prime: continuous operation with load variation.
- Continuous: constant load for long periods.
Choosing the wrong regime reduces service life and may void warranties.
3. Starting Inductive Loads
Electric motors require starting current 3 to 7 times nominal current. The generator must support this peak without excessive voltage drop.
Inadequate sizing can cause:
- Undervoltage;
- Protection tripping;
- Frequency fluctuation;
- Alternator overheating.
4. Regulation System
- AVR (Automatic Voltage Regulator): voltage control.
- Electronic governor: frequency control (Hz).
- Automatic transfer switch (ATS): utility-generator switching.
For sensitive loads (IT, medical equipment), generators with low harmonic distortion (THD < 5%) are recommended.
5. Fuel Consumption and Efficiency
Specific consumption varies with applied load. Diesel engines offer better energy efficiency and durability in intensive applications.
Operating below 30% of nominal load for long periods can cause wet stacking (carbon buildup).
6. Installation Criteria
- Proper grounding;
- Ventilation and heat dissipation;
- Noise control (acoustic enclosure);
- Anti-vibration base.
Technical Conclusion
The generator set must be sized based on actual installed load, operating profile and load characteristics. Oversizing increases capital cost; undersizing compromises stability and service life. Specification must be technical, based on electrical engineering and demand analysis.
