Siemens 5SY7363-8CC — 63 A D-curve MCB for motor and high-inrush loads
The Siemens 5SY7363-8CC is a 3-pole miniature circuit breaker from the SENTRON series, rated 63 A with a D tripping characteristic and a 15 kA breaking capacity per IEC 60947-2. The D-curve (10–20× In) is designed for loads with high inrush currents — motors, transformers, and discharge lighting — where a B or C curve would nuisance-trip on startup. The 15 kA interrupting rating at 440 V AC multi-phase means this breaker clears fault currents up to that level without upstream cascading, sized for industrial panel feeders and machine tool disconnects.
Thermal derating and ambient limits
Rated 63 A at 35 °C ambient; at 40 °C derate to 59.54 A, at 45 °C to 57.71 A, at 50 °C to 55.82 A, at 55 °C to 53.86 A. The breaker is rated for a maximum ambient of 75 °C and a minimum of -40 °C, with humidity limits: 95% RH up to 55 °C, 55% RH to 70 °C, 35% RH to 75 °C. This matters when the panel is in a hot enclosure or near process heat — verify the actual ambient at the mounting location to avoid nuisance tripping at full load.
Integration and mounting
Occupies 3 modular width units (54 mm) on DIN rail, 76 mm deep, 90 mm high. Installation depth is 70 mm. The fastening method is a quick-assembly system — clips onto the rail without tools. Mounting position is any orientation; the supply cord can enter from top or bottom (combined terminal top and bottom). Degree of pollution 3 (conductive pollution, typical for industrial control panels). Touch protection is provided. IP20 with connected conductors — suitable for enclosed panel use only, not for washdown or outdoor exposure.