Motor Power Cable Size Calculator

Cable Size Formula:

\[ \text{Cable Size} = \frac{\text{Current} \times \text{Length} \times \text{Correction Factor}}{\text{Voltage Drop}} \]

Current (A):

Amperes

Length (meters):

meters

Correction Factor:

dimensionless

Voltage Drop (V):

Volts

Required Cable Size:

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1. What is the Cable Size Calculation?

The cable size calculation determines the appropriate cross-sectional area of electrical conductors needed to safely carry current over a specified distance with acceptable voltage drop, based on NEC (National Electrical Code) standards.

2. How Does the Calculator Work?

The calculator uses the cable size formula:

\[ \text{Cable Size} = \frac{\text{Current} \times \text{Length} \times \text{Correction Factor}}{\text{Voltage Drop}} \]

Where:

\( Current \) — Load current in amperes (A)
\( Length \) — Cable run length in meters (m)
\( Correction Factor \) — Adjustment for temperature, grouping, etc.
\( Voltage Drop \) — Maximum allowable voltage drop in volts (V)

Explanation: The equation calculates the minimum conductor size needed to maintain voltage drop within acceptable limits while carrying the specified current over the given distance.

3. Importance of Proper Cable Sizing

Details: Correct cable sizing prevents excessive voltage drop (which can cause equipment malfunction), reduces energy loss, and ensures safe operation by preventing conductor overheating.

4. Using the Calculator

Tips: Enter current in amperes, length in meters, correction factor (typically 1.0 for standard conditions), and maximum allowable voltage drop. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical voltage drop allowance?
A: For most applications, 3% voltage drop is acceptable for branch circuits and 5% for feeder circuits.

Q2: How do I determine the correction factor?
A: Correction factors account for ambient temperature, conductor grouping, and insulation type. Consult NEC tables for specific values.

Q3: Does this calculator account for three-phase systems?
A: This basic version calculates for single-phase. For three-phase, multiply the result by √3 (approximately 1.732).

Q4: What about cable material (copper vs aluminum)?
A: The result is in mm². Aluminum cables typically require about 1.6 times the cross-section of copper for equivalent current carrying capacity.

Q5: Are there other factors to consider?
A: Yes, including short-circuit capacity, installation method, and local regulations. Always consult electrical codes for final sizing.