Diesel Generator Sizing
Estimate diesel generator capacity from continuous load, largest motor starting method, and power factor; recommend common genset ratings.
Key points
Diesel Generator Sizing: Estimate diesel generator capacity from continuous load, largest motor starting method, and power factor; recommend common genset ratings. Formula: S_continuous = P/cosφ×margin | S_start = P_motor×K_start | S_gen = max(S_continuous, S_start). Enter parameters on the DD-CAT IDE online tool page to get results instantly, with a calculation-model diagram that updates with the inputs. Genset capacity is set by both continuous load and the largest motor starting demand; DOL motors are often estimated at 3× motor kW. Starting method matters: star-delta, soft starter, and VFD greatly reduce genset size and voltage dip; prefer soft start / VFD for heavy starts.
Inputs
S_continuous = P/cosφ×margin | S_start = P_motor×K_start | S_gen = max(S_continuous, S_start)Calculation model (updates with parameters)
| Continuous load apparent power | 137.5 kVA | P/cosφ×K = 100 kW/0.80×1.10 |
| Largest motor starting demand | 58.82 kVA | P_m/(η·cosφ_m)×1.5 |
| Required generator capacity | 137.5 kVA | 取连续and启动required的较大Value |
| Recommended genset power | 120 kW | 按常用柴油发motor组Power档向上取整 |
| Corresponding apparent capacity | 150.0 kVA | 按 cosφ=0.80 折算 |
| Continuous load rate | 83 % | 建议 40~80%，避免长期轻载或过载 |
| Starting method factor | 星三角 ×1.5 | 按最大单台Motor starting method选取 |
Engineering notes
- Genset capacity is set by both continuous load and the largest motor starting demand; DOL motors are often estimated at 3× motor kW.
- Starting method matters: star-delta, soft starter, and VFD greatly reduce genset size and voltage dip; prefer soft start / VFD for heavy starts.
- Also check altitude, ambient temperature, intake/exhaust, noise, and fuel tank; fire loads require standby generators per fire codes.
FAQ
- What is Diesel Generator Sizing for?
- Estimate diesel generator capacity from continuous load, largest motor starting method, and power factor; recommend common genset ratings.
- What is the formula for Diesel Generator Sizing?
- Core formula: S_continuous = P/cosφ×margin | S_start = P_motor×K_start | S_gen = max(S_continuous, S_start). The tool returns results instantly using this formula and the selected parameters.
- What engineering notes should I keep in mind when using Diesel Generator Sizing?
- Genset capacity is set by both continuous load and the largest motor starting demand; DOL motors are often estimated at 3× motor kW. Starting method matters: star-delta, soft starter, and VFD greatly reduce genset size and voltage dip; prefer soft start / VFD for heavy starts. Also check altitude, ambient temperature, intake/exhaust, noise, and fuel tank; fire loads require standby generators per fire codes.