1500W Zener TVS — what the ratings mean on the bench
The 1.5SMC440A-M3/57T: That 1500W figure tells you the device can absorb a 2.5A surge at the 602V clamping voltage without failing short — a key spec for protecting a 376V nominal rail from transients like inductive kickback or lightning-coupled spikes. The reverse standoff voltage of 376V means the protected line should never exceed this during normal operation; above that the diode starts conducting leakage current. The clamping voltage of 602V at 2.5A is the voltage the downstream circuit sees during the surge — make sure your load's abs-max rating sits above 602V.
Package and rework — DO-214AB (SMC) in the field
It's a standard two-pad outline — no exposed paddle, no thermal pad to worry about. On a rework station with hot air, you can swap it in under a minute; the body is large enough to grip with tweezers, and the polarity band is clearly marked on the top.