AWG 29 voltage drop calculator
Voltage drop is current times the resistance of the round trip. For AWG 29 the resistance comes straight from the gauge definition and the conductor resistivity.
A
V
Voltage drop
140.070%
- Voltage lost in the cable
- 322.1601 V
- Voltage at the load
- -92.160 V
- Power lost as heat
- 6443.20
- Resistance per metre
- 0.268 467 ohm/m
- Conductor area
- 0.064 216 5 mm2
- Longest run within 3% drop
- 0.64
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 - (29)) / 39) = 0.285 942
- Conductor area = pi * 0.285 942^2 / 4 = 0.064 216 5
- Resistance per metre = 1.724e-8 / (0.064 216 5 * 1e-6) * (1 + 0.00393 * (20 - 20)) = 0.268 467
- Voltage lost in the cable = 2 * 20 * 0.268 467 * 30 = 322.16
- Voltage drop = 322.16 / 230 * 100 = 140.07
- Voltage at the load = 230 - 322.16 = -92.1601
- Power lost as heat = 322.16 * 20 = 6443.2
- Longest run within 3% drop = 0.268 467 > 0 && 20 > 0 ? 230 * 0.03 / (2 * 20 * 0.268 467) : 0 = 0.642 538
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.