Caída de tensión

From Open Source Solar Project
Revision as of 16:12, 15 March 2021 by Alex (talk | contribs) (Created page with "Caída de tensión")
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search
Other languages:
English • ‎español

All wires have a certain amount of resistance that corresponds to their diameter which will cause a certain amount of voltage in the circuit to be lost when current is flowing. High voltage drop in a circuit will cause a lower-than-expected voltage which can create performances issues but does not represent a safety hazard in itself. If a wire is improperly sized it can lead to significant loses in voltage that can cause loads to stop functioning or improper battery charging. Voltage drop must be examined for all circuits in an off-grid PV system.

The calculation can be performed easily by hand, but there are many different free calculators available online that are much quicker - see Special:MyLanguage/Resources. The factors that determine voltage drop in an off-grid PV system are:

  • The maximum circuit current.
  • The resistance of the conductor (wire) based upon its size.
  • The length of the circuit.
  • The operating voltage of the circuit.

The formula for calculating voltage drop is:

Voltage drop = 2 x Circuit current x One-way circuit length (m) x Resistance (Ω/Km) ÷ 1000

The most important value is the percentage voltage drop for the circuit. This is calculated using the formula:

Percentage voltage drop = Voltage drop ÷ Circuit operating voltage x 100

See Wire, overcurrent protection, and disconnect sizing and selection - Phase 4: Voltage drop for recommended voltage drop values for circuits in an off-grid PV system.

Conductor resistance values

A simplified chart with resistances for copper wires.[1]

Copper resistance at 75°C
Size AWG Area Metric equivalent Ω/km
18 0.823 mm² 1 mm² 26.5 Ω
16 1.31 mm² 1.5 mm² 17.3 Ω
14 2.08 mm² 2.5 mm² 10.7 Ω
12 3.31 mm² 4 mm² 6.73 Ω
10 5.261 mm² 6 mm² 4.226 Ω
8 8.367 mm² 10 mm² 2.653 Ω
6 13.30 mm² 16 mm² 1.671 Ω
4 21.15 mm² 25 mm² 1.053 Ω
3 26.67 mm² 0.833 Ω
2 33.62 mm² 35 mm² 0.661 Ω
1 42.41 mm² 50 mm² 0.524 Ω
1/0 53.49 mm² 0.415 Ω
2/0 67.43 mm² 70 mm² 0.329 Ω
3/0 85.01 mm² 95 mm² 0.2610 Ω
4/0 107.2 mm² 120 mm² 0.2050 Ω

Notes/references

  1. NFPA 70 - National Electrical Code 2017: Chapter 9, Table 8