Method
Load-basis kVA calculation with an optional explicit design margin.
Equations
Sb = PPF
Sd = Sb · (1 + m100)
Symbols and units
| Symbol | Quantity | Unit |
|---|---|---|
| Inputs | ||
| P | Active load (after diversity) | kW |
| PF | Power factor | 0–1 |
| m | Design margin (blank = 0) | % |
| Results | ||
| Sb | Base required kVA | kVA |
| Sd | Design required kVA | kVA |
Assumptions and limits
- No standard rating, derating, redundancy or growth assumption is applied.
In practice
- Select the next standard rating at or above Sd, then check loading, ambient derating and redundancy for the project.
Worked example
The input values are the calculator's own verification test, run through the calculator. They show the working; they are not design values.
Inputs
| P | Active load (after diversity) | 800 kW |
| PF | Power factor | 0.8 0–1 |
| m | Design margin (blank = 0) | 20 % |
Results
| Sb | Base required kVA | 1,000 kVA |
| Sd | Design required kVA | 1,200 kVA |
A preliminary check for engineer review, not an engineering approval. The project calculation to the applicable codes, authority requirements and specification governs.