Electrical Wire and Cable Size Calculator
Welcome to this informational page of MPPT Solar. On this page we will teach you how to properly size the electrical wires that will connect the battery and the inverter of our photovoltaic or wind system in order to achieve optimum energy efficiency of the entire system. Thanks to an easy calculation program, inputting the power of the inverter, the total voltage of the batteries and the cable length (+ return trip) we could easily see both the recommended diameter and the power that is dissipated along these cables when passing current.
Electrical Wire Sizing
N.B. To write decimal numbers do not use a comma, but the point (eg 2.5 meters). Note that increasing the voltage of the battery bank, the energy lost on the wires is greatly reduced. Energy losses of up to 1% are acceptable.
What are the wire diameters available on the market?
The diameters commonly available on the market are 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120 and 150. The unit of measurement is square millimeters (mm ²).
What does the abbreviation AWG mean?
AWG is an acronym "American Wire Gauge" and it's a measurement system used mainly in the United States and Canada. It’s possible to find it on the market so here on the left you will find the conversion table of the measurement system AWG in measures of square millimeters.
What is the impact of the wire diameter on the efficiency of my small photovoltaic or wind system?
Many of us already know that higher is the diameter of an electrical wire, lower is the resistance that the wire opposes to the passage of current. For example, a wire of 6 mm² diameter opposes less resistance than a wire cross-section 4 mm². Less resistance means that, according to Ohm's Law, we would have less power loss along the same wire and therefore more useful electrical energy for our needs. For distances up to 50 meters, the standard UNEL 35023, requires that the minimum diameter of an electric wire must not be less than 0.25 mm²/A (ie 4A/mm ²). So an electric wire of 1mm ² is good for a change of currents up to 4A, a wire instead of 2.5 mm ² up to 10A, 4mm ² wire up to 16A, and so on. This is true for wire lengths up to 50 meters
For the design, the legislation requires the use of wires with a minimum cross section of 1.5 mm². The resistivity of copper is 0.0175 ohm × mm²/m. So a copper wire of one meter long and of section size of 1mm² has an electrical resistance of 0.0175 ohms. It is understandable, therefore, that if we have a 1kW inverter and a battery bank voltage of 24V, we will have a loss on that cable about 30W, but if quadruple the diameter of the wire (4mm ²), the loss is reduced four times too. In fact, the loss will be 7.5 W (75% less). The section of a wire is an important parameter in the design of an efficient photovoltaic system.
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