AWG 8 voltage drop calculator
Voltage drop is current times the resistance of the round trip. For AWG 8 the resistance comes straight from the gauge definition and the conductor resistivity.
A
V
Voltage drop
1.075%
- Voltage lost in the cable
- 2.4730 V
- Voltage at the load
- 227.527 V
- Power lost as heat
- 49.46
- Resistance per metre
- 0.002 060 83 ohm/m
- Conductor area
- 8.365 56 mm2
- Longest run within 3% drop
- 83.70
Show the working
- Current = 20
- One-way run length = 30
- Supply voltage = 230
- System = 2
- Conductor = 1.724e-8
- Conductor temperature = 20
- diameter_mm = 0.127 * 92^((36 - (8)) / 39) = 3.263 64
- Conductor area = pi * 3.263 64^2 / 4 = 8.365 56
- Resistance per metre = 1.724e-8 / (8.365 56 * 1e-6) * (1 + 0.00393 * (20 - 20)) = 0.002 060 83
- Voltage lost in the cable = 2 * 20 * 0.002 060 83 * 30 = 2.473
- Voltage drop = 2.473 / 230 * 100 = 1.075 22
- Voltage at the load = 230 - 2.473 = 227.527
- Power lost as heat = 2.473 * 20 = 49.4599
- Longest run within 3% drop = 0.002 060 83 > 0 && 20 > 0 ? 230 * 0.03 / (2 * 20 * 0.002 060 83) : 0 = 83.7042
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- single phase or DC: drop = 2 x I x R per metre x one-way length
- three phase: drop = sqrt(3) x I x R per metre x one-way length
- R per metre = rho / area, corrected for temperature
The factor of two on a single-phase run is because the current goes out and comes back. A three-phase drop uses sqrt(3) because the return currents partly cancel.
This is resistive drop only. On long AC runs at high current, cable reactance adds to it.
Warm conductors have more resistance: at 70 degrees Celsius copper is about 20% more resistive than at 20.