断路器选型计算器 — 公式
## Circuit Breaker Sizing
The breaker must protect the cable while allowing normal load current to flow.
### Sizing Rule
**Minimum breaker rating = Load current x 1.25** (125% per NEC for continuous loads)
Then select the next standard breaker size at or above this value. The breaker rating must also be at or below the cable ampacity to ensure the cable is protected.
The breaker must protect the cable while allowing normal load current to flow.
### Sizing Rule
**Minimum breaker rating = Load current x 1.25** (125% per NEC for continuous loads)
Then select the next standard breaker size at or above this value. The breaker rating must also be at or below the cable ampacity to ensure the cable is protected.
计算示例
A 40 A continuous load with 125% safety factor.
- Minimum rating = 40 x 1.25 = 50 A
- Standard size = 50 A breaker
- Verify that cable ampacity is at least 50 A.