如何计算Wire Sizing
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Wire sizing selects conductor diameter to limit voltage drop and prevent overheating. Code requires ampacity matching and voltage drop limits.
公式
Calculate voltage drop: VD = (2×K×I×L) / (1000×A) for DC or single-phase
- VD
- (2×K×I×L) / (1000×A) for DC or single-phase — (2×K×I×L) / (1000×A) for DC or single-phase
- K
- K value — Variable used in the calculation
- I
- I value — Variable used in the calculation
- L
- L value — Variable used in the calculation
- A
- A value — Variable used in the calculation
- DC
- DC value — Variable used in the calculation
分步指南
- 1Look up ampacity from tables at operating temperature
- 2Calculate voltage drop: VD = (2×K×I×L) / (1000×A) for DC or single-phase
- 3Select wire where VD <3% feeder, <5% combined
例题解析
输入
I = 100 A, L = 50 m, copper wire, assume 60°C ampacity table
结果
AWG 6 (106 A) with ~3.1% drop, marginal
AWG 4 better choice
常见错误注意事项
- ✕Using listed ampacity without derating for temperature or bundling
- ✕Neglecting voltage drop in long feeder runs
常见问题
Why limit voltage drop?
Excessive drop reduces equipment performance, efficiency, and motor starting capability.
How does temperature affect wire sizing?
Higher temperature reduces ampacity; must derate if ambient >30°C.
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