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Understanding Voltage Drop
Voltage drop is the reduction in voltage in an electrical circuit between the source and load. It is important to calculate voltage drop to ensure the efficiency and safety of the electrical system.
Factors Affecting Voltage DropSeveral factors affect voltage drop, including the length of the conductor, the material of the conductor, the cross-sectional area of the conductor, and the current flowing through the conductor.
How to Minimize Voltage DropTo minimize voltage drop, use conductors with larger cross-sectional areas, reduce the length of the conductors, and use materials with lower resistivity such as copper or aluminum.
Voltage Drop Calculation Formula
To calculate the voltage drop, input the current, length, material, AWG, and type of circuit. The calculator will use the appropriate formula to determine the voltage drop.
For AC Single-phase and DC circuits:
$$ V_{drop} = \frac{2 \times I \times \rho \times L}{A} $$
For Three-phase circuits:
$$ V_{drop} = \frac{\sqrt{3} \times I \times \rho \times L}{A} $$
AWG to mm² and Resistance
Use the table below to find the cross-sectional area and resistance for different AWG sizes:
| AWG | Cross-Sectional Area (mm²) | Resistance (Ohms per 1000m) |
|---|---|---|
| 0000 (4/0) | 107.22 | 0.1608 |
| 000 (3/0) | 85.029 | 0.2028 |
| 00 (2/0) | 67.431 | 0.2557 |
| 0 (1/0) | 53.475 | 0.3224 |
| 1 | 42.408 | 0.4066 |
| 2 | 33.631 | 0.5127 |
| 3 | 26.67 | 0.6464 |
| 4 | 21.151 | 0.8152 |
| 5 | 16.773 | 1.028 |
| 6 | 13.302 | 1.296 |
| 7 | 10.549 | 1.634 |
| 8 | 8.366 | 2.061 |
| 9 | 6.634 | 2.599 |
| 10 | 5.261 | 3.277 |
| 11 | 4.172 | 4.132 |
| 12 | 3.309 | 5.211 |
| 13 | 2.624 | 6.571 |
| 14 | 2.081 | 8.285 |
| 15 | 1.65 | 10.448 |
| 16 | 1.309 | 13.174 |
| 17 | 1.038 | 16.612 |
| 18 | 0.823 | 20.948 |
| 19 | 0.6527 | 26.415 |
| 20 | 0.5176 | 33.308 |
| 21 | 0.4105 | 42.001 |
| 22 | 0.3255 | 52.962 |
| 23 | 0.2582 | 66.784 |
| 24 | 0.2047 | 84.213 |
| 25 | 0.1624 | 106.19 |
| 26 | 0.1288 | 133.9 |
| 27 | 0.1021 | 168.85 |
| 28 | 0.081 | 212.92 |
| 29 | 0.0642 | 268.48 |
| 30 | 0.0509 | 338.55 |
| 31 | 0.0404 | 426.9 |
| 32 | 0.032 | 538.32 |
| 33 | 0.0254 | 678.8 |
| 34 | 0.0201 | 855.96 |
| 35 | 0.016 | 1,079.3 |
| 36 | 0.0127 | 1,361 |
| 37 | 0.01 | 1,716.2 |
| 38 | 0.007967 | 2,164.1 |
| 39 | 0.006318 | 2,728.9 |
| 40 | 0.00501 | 3,441.1 |
How much voltage drop is acceptable
The acceptable voltage drop is typically within 5%, but it can vary based on electrical system requirements, load conditions, cable types, length, and national/regional electrical standards.
What is 3% voltage drop rule
This condition causes the load to work harder with less voltage pushing the current. The National Electrical Code recommends limiting the voltage drop from the breaker box to the farthest outlet for power, heating, or lighting to 3 percent of the circuit voltage.