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Feeder Utility

Voltage Drop Calculator

Voltage Drop Calculator supports engineering calculations with transparent assumptions, practical result interpretation, and links to next-step technical resources.

Voltage Drop Visualizer

Formula

ΔV = I × R, with R = ρ(T) × L / A

Single-phase/DC: ΔV ≈ 2 × I × Rcond × L

Drop % = (ΔV / Vsource) × 100

Model assumes resistive drop only (reactance neglected). Suitable for fast feeder screening and conductor trade-off decisions.

Feeder Sketch

Voltage Drop vs One-Way Length

Enter source voltage, current, feeder length, and conductor area to render dynamic voltage-drop curve.

Inputs & Outputs

Source Voltage (V)

Load Current (A)

One-Way Length

Conductor Material

Size Input Mode

Conductor Size

Conductor Temperature (°C)

Target Drop (%)

Material model—

Conductor area—

Resistance per meter—

Equivalent path resistance—

Voltage drop—

Voltage drop (%)—

Load-end voltage—

Feeder I²R loss—

Max one-way length at target—

Area needed at target—

Awaiting valid inputs

Voltage Drop Fundamentals

Voltage drop links wiring resistance to load current and length. It directly affects load-end performance, startup behavior, and thermal losses in feeder conductors.

Engineering Impact

Excessive drop can reduce torque margin, undervolt controls, and increase system losses.

Sizing decisions should account for both nominal and peak operating current.

Design Workflow

Use early in feeder planning to set conductor baseline before final protection and conduit work.

Iterate with temperature and reserve margin assumptions for realistic field behavior.

Equation Reference

Core equation set used by the calculator for fast resistive drop estimates.

Topic	Equation	Meaning
Resistive drop model	ΔV = I × Rpath	Voltage drop is proportional to load current and equivalent path resistance.
Single-phase / DC approximation	ΔV ≈ 2 × I × Rcond × L	Round-trip conductor path is used for two-wire circuits.
Three-phase approximation	ΔV ≈ √3 × I × Rcond × L	Balanced three-phase line-line drop estimate with resistance-only model.
Temperature correction	ρ(T) = ρ20 × (1 + α × (T − 20°C))	Conductor resistance increases with temperature and impacts voltage drop.

Application Workflow Matrix

Map computed drop outputs to feeder design, retrofit, and field troubleshooting decisions.

Scenario	Objective	Recommendation	Critical Checks
Feeder cable sizing	Keep load-end voltage inside acceptable tolerance window	Sweep conductor size and run length together; compare predicted drop against project target percentage before freezing cable spec.	Continuous load profile, terminal temperature, future expansion margin
Panel retrofit extension	Add remote loads without unacceptable voltage sag	Model actual one-way extension length and updated total current before reusing legacy conductor assumptions.	Shared trunk loading, harmonic content, breaker thermal headroom
Commissioning troubleshooting	Screen whether low load voltage can be wiring-related	Use measured current and field-estimated run length to compare expected drop against observed voltage differential.	Measurement point accuracy, connection resistance, supply-side variation