🔌 直流线径计算器（按压降选线，mm² / AWG）DC Wire Size Calculator (by Voltage Drop, mm² and AWG)

使用说明与常见问题How-to & FAQ

「直流线径计算器（按压降选线，mm² / AWG）」是什么？What is the DC Wire Size Calculator (by Voltage Drop, mm² and AWG) tool?

输入直流电压、电流、单程线长、允许压降百分比和导体材料（铜或铝），按往返回路电阻算出所需的最小截面积，并推荐下一档标准公制截面和 AWG 线号，同时给出实际压降和线损功率。适用于太阳能、汽车、房车等低压直流线路。本地处理。Enter the DC voltage, current, one-way cable length, allowed voltage drop and conductor (copper or aluminium) to get the minimum cross-section from the round-trip resistance, the next standard metric size and AWG gauge, and the resulting voltage drop and power loss. For solar, automotive, RV and other low-voltage DC runs. Processed locally.

如何使用「直流线径计算器（按压降选线，mm² / AWG）」？How do I use the DC Wire Size Calculator (by Voltage Drop, mm² and AWG) tool?

在「直流线径计算器（按压降选线，mm² / AWG）」中，填写「系统电压 V」、「电流 A」、「单程线长」、「长度单位」、「允许压降 %」等参数，结果会随输入实时计算并显示在下方。In the DC Wire Size Calculator (by Voltage Drop, mm² and AWG): Fill in "System voltage V", "Current A", "One-way length", "Length unit", "Allowed voltage drop %"; results are recalculated instantly as you type.

公式是什么？What is the formula?

直流回路要算往返两根线：最小截面积 A = 2 × L × I × ρ ÷ ΔV，其中 L 为单程长度 (m)，ρ 为电阻率（铜 0.0172、铝 0.0282 Ω·mm²/m，20 °C），ΔV 为允许压降 (V)。A DC circuit has two conductors, so the minimum area is A = 2 × L × I × ρ / ΔV, with L the one-way length in metres, ρ the resistivity (copper 0.0172, aluminium 0.0282 Ω·mm²/m at 20 °C) and ΔV the allowed drop in volts.

允许压降取多少？What voltage drop should I allow?

常见建议：一般负载 3 %，照明和非关键负载可放宽到 5 %，太阳能电池板到控制器常取 2–3 %，电池到逆变器的大电流线路尽量 1–2 %。Common advice is 3 % for general loads, up to 5 % for lighting and non-critical loads, 2–3 % from solar panels to the controller and 1–2 % for high-current battery to inverter runs.

为什么还要看载流量？Why check ampacity as well?

压降只保证电压够用。短而粗电流大的线路可能压降很小但线缆发热超限，所以必须同时查线缆载流量表并配合适的保险丝。Voltage drop only ensures enough voltage. A short, high-current run can have little drop but still overheat, so also check the ampacity table and fit the right fuse.

能举个计算实例吗？Can you show a worked example?

例如在「直流线径计算器（按压降选线，mm² / AWG）」中填 系统电压 V = 12，电流 A = 20，单程线长 = 5，长度单位 = 米，允许压降 % = 3，导体 = 铜，结果区显示：最小截面积：9.556 mm²；推荐公制截面：10 mm²；该截面实际压降：0.344 V (2.87 %)；线损功率：6.88 W；推荐 AWG：6 AWG (13.3 mm²)；⚠ 只按压降计算。线缆还必须满足载流量（发热）和保险丝要求，并遵守当地电气规范。For example, entering System voltage V = 12, Current A = 20, One-way length = 5, Length unit = m, Allowed voltage drop % = 3, Conductor = Copper in the DC Wire Size Calculator (by Voltage Drop, mm² and AWG) gives: Minimum cross-section: 9.556 mm²; Next metric size: 10 mm²; Drop with that size: 0.344 V (2.87 %); Power lost in cable: 6.88 W; Next AWG size: 6 AWG (13.3 mm²); ⚠ Voltage drop only. The cable must also meet ampacity (heating) and fuse requirements and local…

哪些输入会被检查？Which inputs are validated?

「直流线径计算器（按压降选线，mm² / AWG）」会检查这些输入——「系统电压 V」、「电流 A」、「单程线长」、「允许压降 %」：必须填写，须大于 0；绝对值超过 10¹⁵ 的数也会被拒绝。不符合时结果区显示具体提示，不会给出数字。The DC Wire Size Calculator (by Voltage Drop, mm² and AWG) checks its inputs — "System voltage V", "Current A", "One-way length", "Allowed voltage drop %": required, must be greater than 0; numbers above 10¹⁵ in absolute value are rejected too. When a value fails, the result area names the problem instead of showing a number.

有哪些选项可以调整？What options can I adjust?

「直流线径计算器（按压降选线，mm² / AWG）」的设置：「系统电压 V」默认 12；「电流 A」默认 20；「单程线长」默认 5；「长度单位」可选 米、英尺（默认 米）；「允许压降 %」默认 3；「导体」可选 铜、铝（默认 铜）。每次生成结果都按当前设置处理。Settings in the DC Wire Size Calculator (by Voltage Drop, mm² and AWG) — "System voltage V" default 12; "Current A" default 20; "One-way length" default 5; "Length unit": m, ft (default m); "Allowed voltage drop %" default 3; "Conductor": Copper, Aluminium (default Copper). The result always uses the current settings.

计算结果可以用于作业或工程吗？Can I use the results for homework or engineering?

「直流线径计算器（按压降选线，mm² / AWG）」使用教科书标准公式（公式写在说明和常见问题中），适合学习和估算核对；涉及安全的工程设计请以规范和实测为准。The DC Wire Size Calculator (by Voltage Drop, mm² and AWG) uses standard textbook formulas (given in the description and FAQ), which is good for learning and checking estimates; for safety-critical engineering follow codes and measured values.

「直流线径计算器（按压降选线，mm² / AWG）」免费吗？需要注册吗？Is the DC Wire Size Calculator (by Voltage Drop, mm² and AWG) free? Do I need an account?

「直流线径计算器（按压降选线，mm² / AWG）」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The DC Wire Size Calculator (by Voltage Drop, mm² and AWG) is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.