Generator sizing method
The larger of steady-state design load and the entered starting step is corrected for generic site derating.
Psteady = Prun × Freserve × FgrowthPstep = Prun + PstartingPdesign = max(Psteady, Pstep)Srated = Pdesign/(PF × Kalt × Ktemp)where:
- Pdesign
- Required site active-power output[kW]
- PF
- Load power factor
- Kalt
- Altitude output factor
- Ktemp
- Ambient-temperature output factor
Manufacturer transient and site-rating data govern final selection.
How to use the Generator Sizing Calculator
Estimate generator kW and kVA from running load, largest starting step, power factor, reserve, growth, altitude, and ambient derating. Start by choosing the operating mode, then enter values from nameplates, measurements, or project documents in the units shown. The result updates immediately and keeps intermediate quantities visible for review.
- Confirm the system and calculation mode.
- Enter measured or manufacturer-rated values.
- Review the primary result and intermediate metrics.
- Continue with the related protection or equipment-selection checks.
Calculation method and validation
The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.
How to interpret the result
Use the main result as a starting value and read every supporting metric. Starting step is incremental kW seen by the generator Generic 3% per 500 m above 1000 m altitude screen Generic 1% per 5°C above 40°C temperature screen A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- Starting step is incremental kW seen by the generator
- Generic 3% per 500 m above 1000 m altitude screen
- Generic 1% per 5°C above 40°C temperature screen
Selection limits and next checks
Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions. Replace generic derating with the exact generator datasheet. Motor starting requires manufacturer voltage-dip and frequency-recovery analysis, not kW alone. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.
Continue with ats selection calculatorContinue with maximum demand calculatorContinue with motor starting voltage drop calculator
Assumptions
- Starting step is incremental kW seen by the generator
- Generic 3% per 500 m above 1000 m altitude screen
- Generic 1% per 5°C above 40°C temperature screen
Important Warnings
- Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.
- Replace generic derating with the exact generator datasheet.
- Motor starting requires manufacturer voltage-dip and frequency-recovery analysis, not kW alone.