1500 W surge rating and the protection window it buys
The 1.5SMC200A-E3/57T: The 5.5 A peak pulse current at the clamping voltage tells you the surge the part can absorb; a higher-energy transient than that and the junction exceeds its thermal limit.
DO-214AB (SMC) surface-mount package, also designated SMCJ in the supplier device code — the large tab on the cathode side sinks heat into the board copper, so the effective surge rating depends on the pad area under the part.
Temperature envelope and deployment context
Operates from -65°C to 150°C junction — the wide range covers cold-soak in outdoor telecom cabinets and the self-heating from repetitive surges in an industrial 24 V rail. No power-line protection rating (the part is unidirectional, so it clips only one polarity); use it on signal lines, DC power inputs, or low-voltage AC rails where the transient is positive-going.
The base product number 1.5SMC200 covers the whole family; the - suffix denotes the lead-free / RoHS-compliant version, and the /57T reel code is a packaging variant that does not affect the electrical ratings.