Kalkulator Drop Tegangan

When electrical current flows through a wire, it loses some voltage along the way due to the resistance of the conductor. This is called voltage drop. Understanding and controlling voltage drop is essential for safe, efficient, and code-compliant electrical installations. This calculator uses the NEC (National Electrical Code) 3% guideline and the fundamental physics of conductor resistance to determine whether your cable sizing is adequate.

Why Voltage Drop Matters

Excessive voltage drop causes real problems:

• Equipment malfunction: Motors running at reduced voltage draw higher current, overheat, and fail prematurely.
• Dimming and flickering lights: Voltage-sensitive LEDs and fluorescent fixtures are noticeably affected at drops above 3–5%.
• Overheating conductors: Undersized wires carry excess current (due to the load drawing more current at lower voltage), causing insulation damage and fire risk.
• Reduced efficiency: Power lost as heat in conductors is wasted energy that adds to operating costs.

The NEC recommends a maximum of 3% voltage drop on branch circuits and a combined feeder + branch circuit drop of no more than 5%.

The Formula

For a single-phase AC or DC circuit, the voltage drop across both conductors (supply and return) is:

ΔV = (2 × ρ × I × L) / A

Where:

• ΔV = voltage drop (V)
• ρ = resistivity of conductor material (Ω·m): copper = 1.724×10⁻⁸, aluminum = 2.65×10⁻⁸
• I = current (A)
• L = one-way length (m)
• A = cross-sectional area (m²)

The percentage drop is: ΔV% = (ΔV / Vsource) × 100

AWG Wire Sizes

American Wire Gauge (AWG) is the US standard for wire diameter. Lower numbers mean thicker wire. Common residential wire sizes:

For metric installations, wire size is specified directly in mm².

Copper vs Aluminum

Copper is the preferred conductor for most residential and commercial wiring because:

• Higher conductivity (lower resistivity) means less voltage drop for the same wire size.
• Better mechanical properties — easier to terminate and more resistant to vibration.

Aluminum is used for:

• Large-capacity feeders and service entrance conductors.
• Overhead utility distribution lines.
• Cost savings on very large conductors (aluminum is significantly cheaper than copper per kilogram, though requires a larger size for equivalent performance).

Aluminum conductors require special connectors and anti-oxidant compound at terminations.

Worked Examples

Example 1 — 20A Branch Circuit

A 20A kitchen circuit (AWG 12 copper) runs 25 m to a distant outlet. System voltage is 120 V.

• A = 3.31 mm² = 3.31×10⁻⁶ m²
• ΔV = (2 × 1.724×10⁻⁸ × 20 × 25) / 3.31×10⁻⁶
• ΔV ≈ 5.21 V → 4.3% drop → Warning (exceeds 3% NEC limit)
• Solution: upgrade to AWG 10 (5.26 mm²) → ΔV ≈ 3.28 V → 2.7% ✓

Example 2 — European 230 V Circuit

A 6 mm² copper cable runs 50 m carrying 20A at 230 V.

• ΔV = (2 × 1.724×10⁻⁸ × 20 × 50) / 6×10⁻⁶ ≈ 5.75 V → 2.5% → OK

Three-Phase Circuits

This calculator assumes single-phase (or DC) circuits. For balanced three-phase systems, the formula changes:

ΔV₃φ = (√3 × ρ × I × L) / A

The three-phase voltage drop is approximately 86.6% of the single-phase result for the same wire size, length, and current.

Reference

National Electrical Code (NEC), NFPA 70, Article 210.19(A)(1) FPN No. 4. IEEE Std 399 — Recommended Practice for Industrial and Commercial Power Systems Analysis.