The 1.5SMC91CA BK PBFREE: The 1.5 kW peak pulse rating defines the clamping energy ceiling; 12 A at 125 V clamping is the current the Zener can shunt without degradation under the IEC 61000-4-11 surge profile.
DO-214AB SMC — the rework reality
Surface-mount SMC (DO-214AB) package — the two-terminal barrel fits a standard reflow profile and the wide cathode band makes orientation unambiguous at the bench. At 1.5 kW peak the tab land area matters for thermal relief: the cathode pad should be generously flooded with copper to keep the Zener junction below its 150 °C rating during a fault surge. No exposed paddle, so heatsinking relies on the pad copper area rather than a thermal via farm.
General-purpose transient suppression — not power-line protection
Listed as general-purpose application, and the spec sheet flags power-line protection as not applicable — the 77.8 V standoff sits below the typical 100/120 V line-neutral transient window. For 48 V bus or lower-voltage DC rails this part is well within its working range; for AC line-front it is undersized and a higher-standoff variant from the same series is the right fit.