What the 1500W peak pulse rating means for your protection design
The SMCJ30A-13 is a 1500W (1.5kW) peak pulse power Zener TVS diode in the standard DO-214AB (SMC) surface-mount package. At that waveform, the device clamps a 31A peak pulse current to a maximum of 48.4V, which is the voltage the protected rail sees during the event. For a 30V rail (the reverse standoff voltage, where the diode is effectively off), the 33.3V minimum breakdown voltage means the device starts conducting just above the normal operating range, so it does not load the rail during steady-state conditions. The 48.4V clamp is the ceiling — downstream components rated for at least that peak voltage survive the surge without secondary failure.
The surface-mount body handles the 1500W pulse without external heatsinking; the copper pad area on the PCB under the cathode tab sets the thermal impedance for repetitive surge events. No power line protection (it is a unidirectional Zener, not a steering-diode array), so it is a single-channel clamp for one signal or power rail.