Voltage Drop Formula AC

AC Voltage Drop Formula:

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

Current (I):

Resistance (R):

Ω/km

Reactance (X):

Ω/km

Phase Angle (φ):

Length (L):

Voltage Drop (V_drop):

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1. What is AC Voltage Drop?

AC voltage drop refers to the reduction in voltage that occurs when electrical current flows through a cable or conductor in an alternating current (AC) system. It accounts for both resistance and reactance components of the cable.

2. How Does the Calculator Work?

The calculator uses the AC voltage drop formula:

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

Where:

\( V_{drop} \) — Voltage drop (V)
\( I \) — Current flowing through the cable (A)
\( R \) — Cable resistance per unit length (Ω/km)
\( X \) — Cable reactance per unit length (Ω/km)
\( \varphi \) — Phase angle between voltage and current (°)
\( L \) — Cable length (km)

Explanation: The formula considers both the resistive and reactive components of impedance, with the phase angle determining how much each component contributes to the total voltage drop.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation is essential for ensuring electrical equipment receives adequate voltage, maintaining system efficiency, preventing overheating, and complying with electrical codes and standards.

4. Using the Calculator

Tips: Enter current in amperes, resistance and reactance in Ω/km, phase angle in degrees, and cable length in kilometers. All values must be positive, with phase angle typically between 0° and 90°.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between AC and DC voltage drop?
A: AC voltage drop includes both resistance and reactance components, while DC voltage drop only considers resistance. AC systems have additional losses due to inductive and capacitive effects.

Q2: What is an acceptable voltage drop percentage?
A: Typically, voltage drop should not exceed 3-5% for branch circuits and 1-2% for feeder circuits, depending on local electrical codes and application requirements.

Q3: How does phase angle affect voltage drop?
A: Phase angle determines the power factor. Lower power factors (higher phase angles) increase the reactive component's contribution to voltage drop, potentially requiring larger conductors.

Q4: Where can I find cable resistance and reactance values?
A: Cable manufacturers provide these values in technical datasheets. They depend on conductor material, size, insulation type, and installation method.

Q5: When should I be concerned about voltage drop?
A: Concern arises when voltage drop exceeds code limits, causes equipment malfunction, results in significant power loss, or creates safety hazards due to excessive heating.