The 1.5KE440A-E3/54: That 1500 W rating means the part can absorb a transient surge up to 2.5 A peak pulse current (Ipp) and clamp it to 602 V max — the voltage across the diode during the event stays at or below that figure, protecting downstream silicon. The standoff voltage is 376 V, so the diode does not conduct at normal line voltage below that level; breakdown starts at 418 V minimum.
DO-201AA axial — through-hole fit and temperature range
Housed in a DO-201AA (DO-27) axial leaded package, this is a through-hole part — it solders into a board with leads bent and trimmed, or mounts in a terminal block for high-reliability power supplies and industrial controls. The operating junction temperature range spans -55°C to 175°C, covering cold-start environments and hot enclosures alike. It is a single unidirectional channel — cathode band marked — so polarity matters on the board; reverse connection forward-biases the Zener and defeats the clamping.
Sourcing and compliance documentation
The base product number is 1.5KE440; the -/54 suffix indicates the lead-free / RoHS-compliant finish and the tape-and-reel packaging option (TR).