How to Calculate Cable Voltage Drop2
What is Cable Voltage Drop2?
Calculates voltage loss in electrical cables due to resistance. High losses reduce efficiency and can prevent motor starting.
Formula
Formula: voltage drop = (2 × length × current × resistance) ÷ 1000
Step-by-Step Guide
- 1Current in amperes and cable length
- 2Wire gauge (affects resistance)
- 3Formula: voltage drop = (2 × length × current × resistance) ÷ 1000
- 4Typical target <3% for power, <5% for control
- 5Higher gauge wire reduces drop exponentially
Worked Examples
Input
100A, 50ft, 10 AWG
Result
3.2V drop
Common Mistakes to Avoid
- ✕Using undersized wire to save cost
- ✕Not accounting for temperature derating
Frequently Asked Questions
Why does voltage drop matter?
Reduces equipment voltage, increases losses, causes motors to start slowly, reduces efficiency.
How much does proper wire size cost vs. undersized?
Proper size costs 10-20% more initially but saves 5-10% energy costs over life.
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