Voltage Drop Calculation for Cable

Voltage Drop Formula:

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

Current (I):

Length (L):

Resistivity (ρ):

Ω·m

Cross-sectional Area (A):

m²

Voltage Drop (V_drop):

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1. What is Voltage Drop in Cables?

Voltage drop refers to the reduction in voltage in an electrical circuit between the source and load. It occurs due to the resistance of the conductors and is proportional to the current flowing through them.

2. How Does the Calculator Work?

The calculator uses the voltage drop formula:

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

Where:

\( V_{drop} \) — Voltage drop (V)
\( I \) — Current flowing through the cable (A)
\( L \) — Length of the cable (m)
\( \rho \) — Resistivity of the conductor material (Ω·m)
\( A \) — Cross-sectional area of the conductor (m²)

Explanation: The factor of 2 accounts for the return path in DC or single-phase AC circuits. For three-phase systems, replace 2 with √3 (1.732).

3. Importance of Voltage Drop Calculation

Details: Excessive voltage drop can cause equipment to malfunction, reduce efficiency, and increase energy costs. Electrical codes typically limit voltage drop to 3-5% of the supply voltage.

4. Using the Calculator

Tips: Enter current in amperes, length in meters, resistivity in ohm-meters (1.68×10^-8 Ω·m for copper), and cross-sectional area in square meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical acceptable voltage drop?
A: For most applications, voltage drop should be less than 3% for branch circuits and 5% for feeder and branch circuits combined.

Q2: How does cable material affect voltage drop?
A: Different materials have different resistivities. Copper (1.68×10^-8 Ω·m) has lower resistivity than aluminum (2.65×10^-8 Ω·m), resulting in less voltage drop for the same size.

Q3: Does temperature affect voltage drop?
A: Yes, resistance increases with temperature. The calculator uses resistivity at 20°C. For higher temperatures, adjust resistivity accordingly.

Q4: How do I reduce voltage drop?
A: You can reduce voltage drop by: 1) Using larger cable size, 2) Reducing cable length, 3) Using a material with lower resistivity, or 4) Reducing the current load.

Q5: Is this calculator suitable for AC circuits?
A: This provides a basic estimate. For AC circuits, you should also consider power factor and skin effect, especially at higher frequencies.