Construction Three Phase Load Planning
Three phase power is common on construction sites. It feeds tower cranes, pumps, lifts, compressors, welders, batching plants, and temporary distribution boards. A good load calculation protects cables, breakers, generators, and workers. It also reduces nuisance trips during busy shifts.
The main task is to convert connected equipment into design current. Voltage, power factor, efficiency, demand, diversity, continuous use, and future reserve all affect the answer. A crane motor may start hard, then run at a lower load. Lighting may stay on all day. Pumps may cycle. The calculator separates these items so the estimate is clearer.
Why Demand Matters
Connected load is the sum of all installed loads. Demand load is the part expected to run at the same time. A project rarely uses every tool at full rating together. Demand factor adjusts the connected value. Diversity factor can reduce the combined service requirement when several groups peak at different times.
Continuous loads need special attention. Many designers add a continuous factor for loads expected to run for long periods. Spare capacity is also useful. It allows later site offices, heaters, chargers, or extra tools without rebuilding the feeder.
Using the Result
The current result helps size feeders and protective devices. The kVA result helps compare generators and transformers. The kVAR result shows reactive demand. Lower power factor raises current, even when useful kW stays the same.
The unbalanced phase section is helpful for temporary boards. Uneven single phase loads can increase neutral current. Try to distribute office circuits, heaters, lighting, and small tools evenly across phases. A balanced board runs cooler and wastes less energy.
Practical Site Notes
Always compare calculator results with local electrical codes. Check cable insulation, installation method, ambient temperature, grouping, and voltage drop. Long temporary runs may need larger conductors than current alone suggests. Motor starting current can also require larger breakers or soft starters.
Use equipment nameplates when possible. Use measured current after commissioning. Keep a margin for weather, dust, and rough site conditions. A documented load sheet supports safer inspections, clearer procurement, and better generator rental decisions. Record assumptions beside every result. This makes later checking faster when equipment quantities change or site sequences shift unexpectedly often.