1500W bidirectional Zener — the protection envelope
The 1.5KE440CARL is a bidirectional Zener TVS diode from STMicroelectronics' TRANSIL™ 1.5KE series, rated for 1500W peak pulse power. Its 376V reverse standoff voltage means it stays out of circuit during normal 376V DC bus operation; the breakdown starts at 418V minimum, and the clamping voltage peaks at 776V at the rated 13A peak pulse current. That protection window — standoff, breakdown, clamp — is the full envelope a power rail designer needs to check against the transient immunity of the downstream silicon.
DO-201AA axial — field-swappable with pliers
Through-hole DO-201 axial package. No hot-air station needed — a soldering iron and a pair of flush cutters swap this part on a customer site. The body is keyed by the banded cathode end on the unidirectional version; the bidirectional 1.5KE440CARL has no polarity marking because it does not need one. That saves a reverse-insertion mistake on a board swap.
STMicroelectronics lists the 1.5KE440CARL as obsolete.