Electrical Load Calculator
Three-phase active power from voltage, current, and power factor.
Calculator
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Active power (3φ): 29.44 kW
Formula
Three-phase: P = √3 × V_L × I × cos φ, where V_L is line-to-line voltage (V), I is line current (A), cos φ is power factor.
Example calculation
400 V, 50 A, PF 0.85: P = √3 × 400 × 50 × 0.85 ≈ 29.4 kW.
Engineering notes
For single-phase use P = V × I × cos φ. Include demand and diversity factors for panel sizing; verify with your electrical code.
When to use this calculator
- MCC and panel sizing — calculate the connected load for each motor and sum for feeder and transformer sizing
- Power factor correction — quantify the reactive power (kVAR) to design capacitor banks for PF improvement
- Generator sizing — sum all loads with demand and diversity factors to size a DG set for standby power
- Energy audit — convert measured current and voltage readings to kW for energy consumption analysis
- Project electrical load list — prepare the load schedule during FEED or detailed engineering
Frequently asked questions
- What is power factor and why does it matter for industrial loads?
- Power factor (cos φ) is the ratio of active power (kW) to apparent power (kVA). It represents how efficiently the electrical supply is being converted to useful work. Induction motors and transformers have lagging power factors (0.7–0.9). A low power factor means more current is drawn for the same useful kW, increasing cable, switchgear, and transformer losses. Utilities charge industrial consumers a power factor penalty if the average PF falls below 0.9 or 0.95.
- What is the difference between kW, kVA, and kVAR?
- kW (kilowatts) is the active or real power — the useful work done. kVAR (kilovolt-ampere reactive) is the reactive power — the energy exchanged between the supply and inductive/capacitive loads. kVA (kilovolt-amperes) is the apparent power = √(kW² + kVAR²). The relationship is the power triangle: cos φ = kW/kVA. Generators, transformers, and UPS systems are rated in kVA; motors and heaters are rated in kW.
- How do I calculate electrical load for a motor from its nameplate?
- Motor nameplate shows rated output shaft power in kW or HP, not input power. Input kW = Output kW / motor efficiency. For example, a 22 kW motor with 92% efficiency draws 22/0.92 ≈ 23.9 kW input. The input apparent power = 23.9 / PF kVA. Input current = kVA × 1000 / (√3 × V_L). Always use the rated conditions from the motor datasheet for MCC design.
- What demand factor and diversity factor should I use for load scheduling?
- Demand factor is the ratio of maximum demand to installed connected load (typically 0.7–0.9 for motor loads). Diversity factor accounts for the fact that not all loads operate simultaneously at full load. A typical diversity factor for industrial plants is 0.6–0.8, meaning the transformer/generator only needs to supply 60–80% of the sum of all connected loads. Use local electrical codes or standard tables (IS 1371, IEEE 141) for your application.