1. What is MI Cable Voltage Drop?

Definition: This calculator estimates the voltage drop in mineral insulated (MI) cables based on cable properties and electrical load.

Purpose: It helps electrical engineers and technicians ensure proper voltage levels at the load end of MI cable installations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( VD \) — Voltage drop (volts)
• \( \rho \) — Resistivity of conductor material (ohm-m)
• \( L \) — Length of cable (meters)
• \( I \) — Current flowing through cable (amps)
• \( A \) — Cross-sectional area of conductor (m²)

Explanation: The formula calculates the voltage loss due to conductor resistance over the cable length.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop estimation ensures equipment receives adequate voltage and meets electrical code requirements.

4. Using the Calculator

Tips: Enter the conductor resistivity (default 1.72×10⁻⁸ ohm-m for copper), cable length, current, and conductor area. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is there a factor of 2 in the formula?
A: The factor accounts for the round-trip path of current (both "go" and "return" conductors).

Q2: What's the typical resistivity for MI cables?
A: Copper MI cables use 1.72×10⁻⁸ ohm-m, while nickel MI cables use about 7.8×10⁻⁸ ohm-m.

Q3: How does cable length affect voltage drop?
A: Voltage drop increases linearly with cable length - double the length means double the voltage drop.

Q4: What's the maximum acceptable voltage drop?
A: Most codes recommend ≤3% for branch circuits and ≤5% for feeders, but check local regulations.

Q5: How can I reduce voltage drop?
A: Use larger conductor size, shorter cable runs, or higher voltage systems to minimize voltage drop.