630 A MCCB with high interrupting capacity for line protection
Thermal derating and power dissipation — panel design constraints
The 630 A rating holds only at 40 °C ambient; at 50 °C the breaker must be derated to 593 A, and at 70 °C it drops to 520 A. This derating curve (–) is the spec that governs real-world panel loading — a panel builder sizing busbars and ventilation around the full 630 A at a 50 °C internal ambient will exceed the breaker's thermal limit. Maximum power loss is 162 W at rated current, which drives enclosure heat dissipation requirements.
Interrupting capacity by voltage — selectivity planning
The interrupting capacity varies significantly with system voltage: 242 kA at 240 V, 187 kA at both 415 V and 440 V, 121 kA at 500 V, and 9 kA at 690 V. For 690 V applications, a breaker with higher SCCR at that voltage level would be required. The line protection design optimizes the trip curve for cable and busbar protection rather than motor or generator protection.