Southwire Voltage Calculator

Southwire Voltage Drop Formula:

\[ \text{Drop \%} = \frac{100 \times 1.732 \times L \times I \times R}{V} \text{ (3-phase)} \]

Length (L):

Current (I):

Resistance (R):

ohms/kft

Voltage (V):

Voltage Drop Percentage:

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1. What is the Southwire Voltage Calculator?

The Southwire Voltage Calculator estimates voltage drop percentage in three-phase electrical systems using the standard voltage drop formula. It helps electrical engineers and technicians determine the voltage loss in conductors over distance.

2. How Does the Calculator Work?

The calculator uses the Southwire voltage drop formula:

\[ \text{Drop \%} = \frac{100 \times 1.732 \times L \times I \times R}{V} \text{ (3-phase)} \]

Where:

\( L \) — Length of the conductor in feet
\( I \) — Current in amperes
\( R \) — Resistance in ohms per thousand feet
\( V \) — Voltage in volts
1.732 — Square root of 3 (for 3-phase systems)

Explanation: The formula calculates the percentage of voltage drop based on conductor properties and electrical load characteristics in three-phase systems.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation is essential for ensuring electrical equipment operates within specified voltage ranges, preventing performance issues, equipment damage, and ensuring code compliance in electrical installations.

4. Using the Calculator

Tips: Enter conductor length in feet, current in amperes, resistance in ohms per thousand feet, and system voltage in volts. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is considered an acceptable voltage drop percentage?
A: Generally, a voltage drop of 3% or less for branch circuits and 5% or less for feeder circuits is considered acceptable for most electrical applications.

Q2: Can this calculator be used for single-phase systems?
A: No, this specific formula is for three-phase systems. Single-phase systems use a different formula without the 1.732 multiplier.

Q3: How do I find the resistance value (R) for my conductor?
A: Resistance values can be found in conductor specification tables provided by manufacturers like Southwire, or in NEC Chapter 9, Table 8.

Q4: Why is voltage drop calculation important?
A: Excessive voltage drop can cause motors to overheat, lights to dim, and electronic equipment to malfunction or shut down unexpectedly.

Q5: What factors affect voltage drop?
A: Conductor size, length, material, temperature, current load, and system voltage all affect voltage drop calculations.