AWG 11 voltage drop calculator
Voltage drop is current times the resistance of the round trip. For AWG 11 the resistance comes straight from the gauge definition and the conductor resistivity.
A
V
Voltage drop
2.156%
- Voltage lost in the cable
- 4.9584 V
- Voltage at the load
- 225.042 V
- Power lost as heat
- 99.17
- Resistance per metre
- 0.004 132 03 ohm/m
- Conductor area
- 4.172 29 mm2
- Longest run within 3% drop
- 41.75
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 - (11)) / 39) = 2.304 85
- Conductor area = pi * 2.304 85^2 / 4 = 4.172 29
- Resistance per metre = 1.724e-8 / (4.172 29 * 1e-6) * (1 + 0.00393 * (20 - 20)) = 0.004 132 03
- Voltage lost in the cable = 2 * 20 * 0.004 132 03 * 30 = 4.958 43
- Voltage drop = 4.958 43 / 230 * 100 = 2.155 84
- Voltage at the load = 230 - 4.958 43 = 225.042
- Power lost as heat = 4.958 43 * 20 = 99.1687
- Longest run within 3% drop = 0.004 132 03 > 0 && 20 > 0 ? 230 * 0.03 / (2 * 20 * 0.004 132 03) : 0 = 41.7471
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.