The electrical load capacity of wires is a concern for many people before purchasing them. In daily life, commonly used wire gauges include 1 square millimeter (mm²), 1.5 mm², 2.5 mm², 4 mm², and 6 mm² wires. Now, let's delve into the details about the wattage that these wires can handle, specifically for 1 mm², 1.5 mm², 2.5 mm², 4 mm², and 6 mm² wires.
The allowable long-term load currents for copper core wires of different gauges are as follows:
For 1 square millimeter (mm²) copper core wire, the allowable long-term load current is: 8A to 12A.
For 1.5 mm² copper core wire, the allowable long-term load current is: 12A to 15A.
For 2.5 mm² copper core wire, the allowable long-term load current is: 16A to 25A.
For 4 mm² copper core wire, the allowable long-term load current is: 25A to 32A.
For 6 mm² copper core wire, the allowable long-term load current is: 32A to 40A.
A 1 square millimeter copper wire can carry a current of up to 6 amps. For aluminum core cables, a 1 square millimeter wire can typically handle a current of 3 to 5 amps.
The amperage that a copper wire can carry is related to factors such as the cable length, the method of cable installation, and the ambient temperature of the cable's usage environment. Indoors, for copper wires with a cross-sectional area of less than 6 square millimeters, it is generally safe for the current per square millimeter not to exceed 10 amps.
Using the "electrical engineering empirical method" for estimation:
Since each square millimeter of cross-sectional area of copper core wire can typically carry a rated current of 4.5 to 5 amps, and in a single-phase 220V circuit, each kilowatt of power corresponds to approximately 4.5 amps of current, while in a three-phase circuit (including three-phase four-wire systems), each kilowatt of power corresponds to approximately 2 amps of current, the following selections can be made: For single-phase circuits, basically, 1 square millimeter of wire is needed for every kilowatt of power. In three-phase circuits, 1 square millimeter of copper wire can carry a current corresponding to approximately 2 to 2.5 kilowatts of power.
Although 1.5mm² electrical wires are not as commonly used as 2.5mm² wires, they still have their own load limits. The method for calculating the current capacity of a 1.5mm² wire is as follows: Household electrical wires are generally single-phase, and their maximum power tolerance (Pm) can be calculated as follows, using 1.5mm² as an example:
Pm = Voltage (U) × Current (I) = 220V × 22A = 4840W. Taking a safety coefficient of 1.3, the allowable power (P) for long-term operation is: P = Pm ÷ 1.3 = 4840 ÷ 1.3 = 3723W.
Therefore, a 1.5mm² electrical wire can tolerate a load of 3723 watts.
The safe current carrying capacity of a 2.5mm² electrical wire is approximately 22A.
Depending on the line voltage, which is commonly 380V or 220V, the load capacity will differ:
For 220V single-phase AC: P = IUcosφ = 220 × 22 × 0.9 = 4.4kW
For 380V three-phase AC: P = √3IUcosφ = 1.732 × 380 × 22 × 0.9 = 13kW
According to electrical rules of thumb, a 4mm² copper wire can be considered equivalent to a 6mm² aluminum wire in terms of its safe current-carrying capacity, which is seven times its cross-sectional area. Therefore, the safe current-carrying capacity of a 4mm² copper wire is 6x7=42A.
If it is a three-phase system, the power calculation is as follows:
P = 1.732UIcosφ = 1.732x0.38x42x0.85 = 23kW (calculated using three-phase utility power, with a power factor of 0.85).
If it is a single-phase system, the power calculation is as follows:
P = UIcosφ = 0.22x42x0.65 = 6kW (calculated using single-phase utility power, with a power factor of 0.65).
The diameter of a power line and the power it can transmit are not directly related. Generally speaking, a 6mm² wire is more than sufficient for use as an air conditioning wire. On construction sites, a 10x6+1x4 cable is commonly used for maintenance power. As for the current-carrying capacity, based on my construction experience, this type of cable is typically controlled by a 63A circuit breaker. A 6mm² aluminum wire can handle 6kW, while a 6mm² copper wire can handle 10kW.
One square millimeter of copper core can withstand a current of 7A.
Therefore, the current capacity of a 10mm² copper core can be calculated as follows: 10 × 7 = 70A.
For 220V single-phase appliances, one kilowatt corresponds to a current of approximately 4.55A.
We can then determine the wattage capacity of a 10mm² copper core by dividing its current capacity by the current that one square millimeter of copper core can withstand, as follows: 70A ÷ 4.55 ≈ 15.4KW.