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Electrical Parameters
Installation Conditions
Cable Sizing Result
Recommended Cable Size
4 mm²
Ampacity: 35 A (after derating)
Voltage Drop
2.15% (4.7V)
Power Loss
105.0 W
Derating Factor
100%
Efficiency
97.9%
Alternative Cable Sizes
2.5 mm²(25 A, 3.44% drop)
Does not meet requirements6 mm²(50 A, 1.43% drop)
Higher safety margin, lower voltage dropCalculation Steps
1.
Continuous load factor: 20 A × 1.25 = 25.0 A
2.
Temperature derating (30°C at 75°C): 1.000
3.
Grouping derating (1 cables): 1.000
4.
Installation method factor: 1.000
5.
Total derating factor: 1.000
6.
Required ampacity (before derating): 25.0 / 1.000 = 25 A
7.
Selected cable size (ampacity): 2.5 mm² (25 A before derating)
8.
Single-phase voltage drop: Vd = 2 × I × R × cos(φ=0.9) = 2 × 20 × 0.2100 × 0.9 = 7.56 V
9.
ℹ️ Power factor 0.9 applied to voltage drop calculation
10.
Voltage drop percentage: 3.44%
11.
Power loss: 168.00 W
12.
⚠️ Voltage drop 3.44% exceeds limit 3% - larger cable needed!
13.
Upgraded to 4 mm² to meet voltage drop requirement
Cable Sizing Guidelines
NEC Requirements:
- •Branch circuits: Max 3% voltage drop
- •Feeders: Max 3% voltage drop
- •Total: Max 5% from service to load
- •Continuous loads: 125% of rated current
Derating Factors:
- •Temperature: Higher ambient = lower ampacity
- •Grouping: More cables = more heat = lower ampacity
- •Installation: Enclosed = less cooling = lower ampacity