Clamping performance and the 1500 W rating
The 1.5SMC33A_R1_00001: Rated for 1500 W peak pulse power at 10/1000 µs waveform — this is the standard TVS power rating for the DO-214AB package, and it determines how much transient energy the diode can absorb before the junction fails. Clamps at 45.7 V maximum when conducting 33 A peak pulse current (Ipp). Unidirectional — one channel, so it protects a single rail against positive overvoltage transients. For bidirectional protection on AC lines or bipolar rails, you would need two devices or a bidirectional variant.
The copper pad area under the cathode tab sets the thermal resistance; a larger pad pulls heat away from the junction during repetitive pulse events.