How Do You Calculate Voltage Drop And Cable Size

Voltage Drop and Cable Size Formulas:

\[ Vd = \frac{2 \times L \times I \times \rho}{A} \] \[ A = \frac{2 \times L \times I \times \rho}{Vd} \]

Length (L):

Current (I):

Resistivity (ρ):

ohm m

Calculation Type:

Cable Size (A):

mm²

Result:

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1. What is Voltage Drop and Cable Size Calculation?

Voltage drop calculation determines the reduction in voltage in an electrical circuit due to the resistance of the conductors. Cable size calculation determines the appropriate conductor cross-sectional area to limit voltage drop to acceptable levels.

2. How Does the Calculator Work?

The calculator uses the following formulas:

\[ Vd = \frac{2 \times L \times I \times \rho}{A} \] \[ A = \frac{2 \times L \times I \times \rho}{Vd} \]

Where:

\( Vd \) — Voltage drop (V)
\( L \) — Length of the cable (m)
\( I \) — Current (A)
\( \rho \) — Resistivity of the conductor material (ohm m)
\( A \) — Cross-sectional area of the conductor (mm²)

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

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation ensures electrical equipment operates within specified voltage limits, prevents performance issues, and maintains safety standards in electrical installations.

4. Using the Calculator

Tips: Enter all required values with appropriate units. Select whether you want to calculate voltage drop or cable size. Ensure all values are positive and within reasonable ranges for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical resistivity value for copper?
A: The resistivity of copper is approximately 1.724 × 10⁻⁸ ohm m at 20°C.

Q2: What is the typical resistivity value for aluminum?
A: The resistivity of aluminum is approximately 2.82 × 10⁻⁸ ohm m at 20°C.

Q3: What is an acceptable voltage drop percentage?
A: Generally, voltage drop should not exceed 3% for branch circuits and 5% for feeder and branch circuits combined according to most electrical codes.

Q4: Does temperature affect resistivity?
A: Yes, resistivity increases with temperature. The values given are typically for 20°C and should be adjusted for different operating temperatures.

Q5: When should I use the √3 factor instead of 2?
A: Use √3 for three-phase systems instead of the factor 2 used for single-phase systems.