Voltage Drop Calculation For Ac Cable

AC Cable Voltage Drop Formula:

\[ V_{drop} = \sqrt{3} \times I \times (R \cos \varphi + X \sin \varphi) \times L \]

Current (I):

Resistance (R):

Ω/km

Reactance (X):

Ω/km

Power Factor (cos φ):

(0-1)

Cable Length (L):

Voltage Drop (V_drop):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is AC Cable Voltage Drop?

AC cable voltage drop refers to the reduction in voltage that occurs when electrical current flows through a cable due to the resistance and reactance of the conductor. It's an important consideration in electrical system design to ensure proper voltage levels at the load.

2. How Does the Calculator Work?

The calculator uses the AC cable voltage drop formula:

\[ V_{drop} = \sqrt{3} \times I \times (R \cos \varphi + X \sin \varphi) \times L \]

Where:

\( V_{drop} \) — Voltage drop (V)
\( \sqrt{3} \) — Three-phase system constant (1.732)
\( I \) — Current (A)
\( R \) — Resistance per unit length (Ω/km)
\( \cos \varphi \) — Power factor
\( X \) — Reactance per unit length (Ω/km)
\( L \) — Cable length (km)

Explanation: The formula accounts for both resistive and reactive components of voltage drop in three-phase AC systems, with the power factor determining the phase relationship between voltage and current.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation ensures that electrical equipment receives adequate voltage for optimal operation, prevents equipment damage, maintains system efficiency, and complies with electrical codes and standards.

4. Using the Calculator

Tips: Enter current in amperes, resistance and reactance in ohms per kilometer, power factor (between 0 and 1), and cable length in kilometers. All values must be positive, with power factor between 0 and 1 inclusive.

5. Frequently Asked Questions (FAQ)

Q1: What is the acceptable voltage drop percentage?
A: Typically, voltage drop should not exceed 3-5% from source to load for branch circuits, and 5-8% for feeder and branch circuits combined, depending on local electrical codes.

Q2: How does power factor affect voltage drop?
A: Lower power factors increase the reactive component of voltage drop, resulting in higher total voltage drop for the same current and cable parameters.

Q3: When is voltage drop calculation critical?
A: Critical for long cable runs, high current applications, sensitive electronic equipment, and systems where motor starting voltage dip must be considered.

Q4: How can I reduce voltage drop?
A: Use larger cable cross-sections, reduce cable length, improve power factor, use higher system voltage, or install voltage regulation equipment.

Q5: Is this calculator suitable for DC systems?
A: No, this calculator is specifically for three-phase AC systems. For DC systems, use \( V_{drop} = 2 \times I \times R \times L \) (accounting for both conductors).