1. What is a Cable Size Selection Calculator?

Definition: This calculator determines the minimum cross-sectional area of a cable needed based on current, length, resistivity, and maximum allowable voltage drop.

Purpose: It helps electrical engineers and technicians select appropriate cable sizes to ensure safe and efficient power distribution.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( A \) — Cross-sectional area (m²)
• \( I \) — Current (amps)
• \( L \) — Length of cable (meters)
• \( \rho \) — Resistivity of conductor material (ohm-m)
• \( V_D \) — Maximum allowable voltage drop (volts)

Explanation: The formula calculates the minimum conductor size needed to maintain voltage drop within acceptable limits for a given current over a specified distance.

3. Importance of Proper Cable Sizing

Details: Correct cable sizing prevents excessive voltage drop, reduces energy loss, minimizes heat generation, and ensures electrical safety.

4. Using the Calculator

Tips: Enter the current in amps, cable length in meters, resistivity (default 1.68×10⁻⁸ ohm-m for copper), and maximum allowable voltage drop. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the typical resistivity value for copper?
A: Copper has a resistivity of about 1.68×10⁻⁸ ohm-m at 20°C. For aluminum, use 2.65×10⁻⁸ ohm-m.

Q2: How do I determine acceptable voltage drop?
A: Generally, 3% for branch circuits and 5% for feeder circuits of the supply voltage is acceptable.

Q3: Does this account for temperature effects?
A: No, resistivity increases with temperature. For high-temperature applications, use adjusted resistivity values.

Q4: How do I convert the result to AWG or mm²?
A: Use standard wire gauge tables to find the nearest standard size equal to or larger than your calculated area.

Q5: Should I consider other factors in cable selection?
A: Yes, also consider current carrying capacity, installation method, ambient temperature, and short-circuit protection.