💡 Electrical Power Calculation Formulas
DC Power: P = V × I
Where: P = Power (Watts), V = Voltage (Volts), I = Current (Amperes)
AC Power:
Real Power: P = V × I × cos(φ)
Reactive Power: Q = V × I × sin(φ)
Apparent Power: S = V × I
Power Factor: PF = cos(φ)
Three-Phase Power:
Star Connection: P = √3 × V_L × I_L × cos(φ)
Delta Connection: P = √3 × V_L × I_L × cos(φ)
Where: V_L = Line Voltage, I_L = Line Current
Energy Cost: Cost = P(kW) × Time(hours) × Rate($/kWh)
Annual Cost = Daily Cost × Operating Days
Power Factor Correction:
Required kVAR = P × (tan(φ₁) - tan(φ₂))
Capacitor Value: C = kVAR / (2πfV²) × 10⁶ (μF)
Motor Sizing:
Required HP = Load HP / (Efficiency × Service Factor)
Full Load Current = (HP × 746) / (V × √3 × Efficiency × PF)
Short Circuit Current:
I_sc = V / √(R² + X²)
Peak Current = √2 × I_sc × (1 + e^(-R/L × t))
Harmonic Analysis:
THD = √(Σ(I_h²)) / I_1 × 100%
Where: I_h = harmonic current, I_1 = fundamental current
🎯 Key Applications
- Power System Design: Calculate loads, sizing equipment, and ensuring adequate capacity
- Energy Efficiency: Identify energy savings opportunities and optimize power factor
- Motor Applications: Size motors correctly and analyze starting performance
- Protection Coordination: Calculate fault currents and select protective devices
- Power Quality: Assess system performance and identify issues
- Load Management: Optimize demand and reduce energy costs
- Renewable Integration: Analyze grid impact and ensure compatibility
⚠️ Important Considerations
- Always use proper units and maintain unit consistency
- Consider temperature effects on resistance and component ratings
- Account for harmonics and their impact on system performance
- Verify calculations against actual measurements when possible
- Consider safety factors in all design calculations
- Follow local electrical codes and standards (NEC, IEC, etc.)