AWG 24 voltage drop calculator
Voltage drop is current times the resistance of the round trip. For AWG 24 the resistance comes straight from the gauge definition and the conductor resistivity.
A
V
Voltage drop
43.935%
- Voltage lost in the cable
- 101.0500 V
- Voltage at the load
- 128.950 V
- Power lost as heat
- 2021.00
- Resistance per metre
- 0.084 208 3 ohm/m
- Conductor area
- 0.204 73 mm2
- Longest run within 3% drop
- 2.05
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 - (24)) / 39) = 0.510 559
- Conductor area = pi * 0.510 559^2 / 4 = 0.204 73
- Resistance per metre = 1.724e-8 / (0.204 73 * 1e-6) * (1 + 0.00393 * (20 - 20)) = 0.084 208 3
- Voltage lost in the cable = 2 * 20 * 0.084 208 3 * 30 = 101.05
- Voltage drop = 101.05 / 230 * 100 = 43.9348
- Voltage at the load = 230 - 101.05 = 128.95
- Power lost as heat = 101.05 * 20 = 2021
- Longest run within 3% drop = 0.084 208 3 > 0 && 20 > 0 ? 230 * 0.03 / (2 * 20 * 0.084 208 3) : 0 = 2.048 49
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.