The 1.5KE91A-E3/73: That 1.5 kW rating means it can absorb a 12 A transient and clamp it to 125 V without failing, provided the pulse duration stays within the 1 ms window. For a 24 V or 48 V DC bus with a 77.8 V reverse standoff, this part sits below the rail's normal operating peak and only conducts during an overvoltage event.
Breakdown window and clamping ceiling
Breakdown is specified at 86.5 V minimum, with the reverse standoff at 77.8 V — a 8.7 V margin between the maximum continuous voltage and the point where the device starts conducting. That guard band keeps the TVS out of the circuit during normal ripple and line regulation. A downstream DC-DC converter with a 100 V abs-max input would need additional protection; one rated for 150 V has comfortable margin.
Through-hole package and temperature range
The DO-201AA axial-lead package is a through-hole format that handles the thermal cycling of the 1500 W pulse by sinking heat into the PCB copper and the lead wire itself. The Tape & Box packaging is a standard reel-alternative format for axial parts, common in through-hole assembly lines that feed from a tube or box rather than a tape reel.