What the 500W rating buys you in the field
That 500W number is the energy it can dump in a single surge — enough to clamp a 2.8A pulse at 178.8V without failing. For a field repair, this means the part handles the kind of transient you see on 48V telecom lines or 120VAC industrial control loops where a relay coil kick or lightning-coupled spike tries to punch through the silicon.
Voltage thresholds and margin check
Breakdown starts at 123.5V minimum, and clamping hits 178.8V maximum at the peak pulse current of 2.8A. The gap between standoff and clamping gives you about 80V of headroom; if your rail sits at 100V nominal, you have margin. If the rail is 120V, the diode starts to conduct during normal operation and you cook it.
Active production — no LTB panic
Microchip lists the 1N6133A as Active. The axial through-hole package (B, Axial) is a standard footprint. For a BOM line, this part is orderable today.
Through-hole package — field-swappable
Axial leaded package (B, Axial). Two leads, polarity marked by the cathode band (though bidirectional means you can install it either way and it still clamps both polarities). On site, you can swap it with a soldering iron and a pair of cutters; no hot-air station, no reflow profile.