Siemens 5SY4303-8CV MCB, 3P D3, 15kA at 400V

The Siemens 5SY4303-8CV is a 3-pole miniature circuit breaker (MCB) with a D tripping characteristic, rated at 3 A and a 15 kA breaking capacity at 400 V AC. The D-curve means it tolerates high inrush currents — typically used for motor, transformer, or lighting ballast circuits where the start-up surge would nuisance-trip a B or C curve. The 15 kA Icu at 400 V AC is the maximum fault current it can safely interrupt under short-circuit conditions without welding its contacts or rupturing the arc chamber.