1. What is the Conductor Size Calculation?

The conductor size calculation determines the appropriate cross-sectional area of electrical conductors needed for motor circuits on transformer secondaries, considering current, distance, and allowable voltage drop.

2. How Does the Calculator Work?

The calculator uses the conductor size formula:

Where:

• \( Current \) — Motor full load current in amperes
• \( Length \) — One-way length of conductor in meters
• \( Correction Factor \) — Adjustment for temperature, bundling, etc.
• \( Voltage Drop \) — Maximum allowable voltage drop in volts

Explanation: The formula calculates the minimum conductor size needed to maintain voltage drop within acceptable limits for proper motor operation.

3. Importance of Proper Conductor Sizing

Details: Correct conductor sizing ensures motor starting and running performance, prevents excessive voltage drop, reduces energy losses, and maintains equipment safety.

4. Using the Calculator

Tips: Enter motor full load current in amperes, one-way conductor length in meters, appropriate correction factor (typically 1.0-1.5), and maximum allowable voltage drop (usually 3-5% of system voltage).

5. Frequently Asked Questions (FAQ)

Q1: What is a typical correction factor value?
A: For single conductors in free air at 30°C, use 1.0. Higher values account for temperature, bundling, or conduit fill.

Q2: What voltage drop is acceptable?
A: Typically 3% for branch circuits, 5% for feeders. Consult local electrical codes.

Q3: Should I use one-way or round-trip length?
A: Use one-way length as the formula already accounts for the round-trip path.

Q4: How does transformer secondary voltage affect this?
A: The calculation is independent of voltage level but assumes the voltage drop is measured at the motor terminals.

Q5: What about motor starting current?
A: For large motors, consider separate starting current calculations as they may require larger conductors.