Voltage Drop Calculator South Africa

Voltage Drop Formula:

\[ VD = 2 \times \rho \times L \times I / A \]

Resistivity (ρ):

ohm-m

Cable Length (L):

meters

Current (I):

amps

Conductor Area (A):

m²

Voltage Drop (VD): volts

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1. What is a Voltage Drop Calculator for South Africa?

Definition: This calculator estimates the voltage drop in electrical circuits based on conductor properties and current flow, following South African standards.

Purpose: It helps electricians and engineers ensure proper voltage levels throughout electrical installations in compliance with SANS 10142-1.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ VD = 2 \times \rho \times L \times I / A \]

Where:

\( VD \) — Voltage drop (volts)
\( \rho \) — Resistivity of conductor material (ohm-m)
\( L \) — Length of cable (meters)
\( I \) — Current flowing through conductor (amps)
\( A \) — Cross-sectional area of conductor (m²)

Explanation: The factor of 2 accounts for the return path in single-phase systems. For three-phase systems, use √3 instead of 2.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation ensures electrical equipment receives adequate voltage, prevents overheating, and complies with South African regulations (max 5% drop for lighting, 10% for other circuits).

4. Using the Calculator

Tips:

Default resistivity is for copper (1.72×10⁻⁸ ohm-m). Use 2.82×10⁻⁸ for aluminum.
Enter cable length (one-way distance).
Current should be the maximum expected load current.
Conductor area is the actual cross-sectional area of the wire.

5. Frequently Asked Questions (FAQ)

Q1: What's the maximum allowed voltage drop in South Africa?
A: SANS 10142-1 specifies maximum 5% for lighting circuits and 10% for other circuits from the point of supply to any point of utilization.

Q2: How do I convert mm² to m² for conductor area?
A: Divide mm² by 1,000,000 (e.g., 2.5mm² = 2.5×10⁻⁶ m²).

Q3: When would I use the three-phase formula?
A: For three-phase systems, replace the factor 2 with √3 (approximately 1.732).

Q4: What's typical resistivity for copper conductors?
A: 1.72×10⁻⁸ ohm-m at 20°C for pure copper. Higher for alloys or at elevated temperatures.

Q5: How does temperature affect voltage drop?
A: Higher temperatures increase resistivity and thus voltage drop. For precise calculations, use resistivity values at operating temperature.