1500W bidirectional TVS — the clamping number that decides the rail
The 1.5KE91CA B0G is a 1500 W bidirectional Zener TVS from the 1.5KE series, designed to clamp transients on unipolar or bipolar signal lines where the working voltage sits at 77.8 V reverse standoff. The 86.5 V minimum breakdown means the device stays out of conduction below that threshold, so a nominal 48 V or 60 V rail sees no leakage impact during normal operation. A 125 V clamp on a 77.8 V rail gives roughly 60 % headroom above the working voltage, a typical margin for industrial 48 V bus or 72 V battery lines.
Through-hole DO-201 — axial-lead footprint for retrofit and high-reliability boards
The DO-201AA / DO-27 axial-lead package is a standard through-hole form factor that mates with existing PCB layouts for the 1.5KE series. The 0.050-inch lead diameter and 1.0-inch body length are common across the family, so a BOM swap from a different 1.5KE voltage variant requires no board spin — only the breakdown voltage changes. The wide Tj envelope also means the TVS can be placed close to the transient source (e.g., a relay coil or motor brush) without derating for self-heating at modest duty cycles.
No power-line protection — intended for signal and DC bus transient suppression
The part is explicitly listed with Power Line Protection = No. This means it is not rated for direct AC mains or high-energy surge events per IEC 61000-4-5 Class 4; instead it targets secondary-side DC buses, communication lines, and low-impedance signal paths where the 1500 W peak pulse capability handles ESD, inductive kickback, and lightning-induced transients on outdoor cabling. For mains-side protection, a higher-energy MOV or gas tube is the correct first-stage device.