What the 1500 W peak pulse rating means for your rail
The 1.5KE43A R0G: That 1500 W figure is the product of the clamping voltage and the peak pulse current — at the 59.3 V clamp, the device handles 26 A before the junction absorbs the transient. The 36.8 V reverse standoff voltage means the diode stays transparent on a nominal 36 V bus — it does not conduct until the transient pushes the line above 40.9 V (the minimum breakdown voltage). Below that threshold, the leakage current is negligible for most general-purpose protection circuits.
The axial leads require a hole diameter of roughly 1.0 mm on the PCB. Keep the trace width from the protected rail to the anode short and wide — the inductance in a long skinny trace adds voltage drop during the fast rising edge of a 10/1000 µs pulse.