The 1.5KE39CA-T: The 37.1V minimum breakdown ensures the device starts clamping before the voltage reaches a level that would stress typical 40V-rated downstream components. The 53.9V clamping voltage at 28A peak pulse current defines the maximum voltage the load sees during a surge — a downstream capacitor rated at 63V or higher provides adequate margin.
Housed in a DO-201AA/DO-27 axial-lead through-hole package, the device suits high-reliability boards where solder-joint inspection is required and where the leaded form factor provides better thermal conduction to the PCB than a surface-mount equivalent.