Cable Voltage Drop Calculation

Voltage Drop Formula:

\[ \text{Drop %} = \frac{I \times R \times L \times 2}{V} \times 100 \]

Current (I):

Resistance (R):

Ω/km

Length (L):

Voltage (V):

volts

Voltage Drop Percentage:

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1. What is Voltage Drop Calculation?

Voltage drop calculation determines the reduction in voltage in an electrical circuit between the source and load. It's crucial for ensuring proper operation of electrical equipment and compliance with electrical codes.

2. How Does the Calculator Work?

The calculator uses the voltage drop formula:

\[ \text{Drop %} = \frac{I \times R \times L \times 2}{V} \times 100 \]

Where:

\( I \) — Current in amperes (A)
\( R \) — Resistance per unit length in ohms per kilometer (Ω/km)
\( L \) — Length of cable in kilometers (km)
\( V \) — Supply voltage in volts (V)
\( 2 \) — Factor for round trip (out and return)

Explanation: The formula calculates the percentage voltage drop based on current flow, cable resistance, cable length, and supply voltage.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation ensures electrical equipment receives adequate voltage for optimal performance, prevents equipment damage, and complies with electrical safety standards and regulations.

4. Using the Calculator

Tips: Enter current in amperes, resistance in Ω/km, cable length in kilometers, and supply voltage in volts. All values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is an acceptable voltage drop percentage?
A: Typically, voltage drop should not exceed 3% for branch circuits and 5% for feeder and branch circuits combined, but local codes may vary.

Q2: Why multiply by 2 in the formula?
A: The factor of 2 accounts for the round trip path - current flowing to the load and returning through the neutral or ground.

Q3: How do I find cable resistance values?
A: Cable resistance values are typically provided in manufacturer datasheets or electrical reference tables based on cable size and material.

Q4: Does temperature affect voltage drop?
A: Yes, cable resistance increases with temperature, which can increase voltage drop. Calculations should consider operating temperature.

Q5: When is voltage drop calculation critical?
A: Critical for long cable runs, high current applications, sensitive electronic equipment, and installations where voltage stability is essential.