What this 1500 W Zener TVS protects
The 1.5KE170A-T: It clamps a 145 V reverse standoff voltage to 234 V max at a peak pulse current of 6.4 A, which means a 48 V or 72 V bus that sees a 1.5 kW surge gets held below the downstream component's abs-max rating. The part is obsolete per the manufacturer, so new-design sourcing goes through independent distribution channels. For a repair or a BOM fill on an existing board, the DO-201 axial package (also known as DO-27) is a through-hole footprint that hand-solders easily — no hot-air profile needed.
Voltage ratings and the clamping decision
The reverse standoff voltage (working voltage) is 145 V — the TVS draws negligible leakage below this level. Breakdown occurs at 162 V min, and clamping is 234 V max at the full 6.4 A peak pulse current. The gap between standoff and clamp (roughly 89 V) is the voltage the TVS absorbs across its dynamic resistance during the surge event. The 1500 W rating is derated above 25°C per the standard power-temperature curve for a DO-201 package — at 175°C the peak pulse power drops to near zero, so the thermal margin at the operating ambient must be checked against the surge duty cycle.
Sourcing an obsolete TVS diode
Diodes Incorporated lists the 1.5KE170A-T as obsolete. For a BOM that needs this exact clamping voltage and package, the through-hole DO-201 footprint is shared across the entire 1.5KE series — a parametric search for 1500 W, 145 V standoff, unipolar, DO-201 will turn up active alternatives from multiple suppliers, though pinout and electrical limits should be cross-checked against the original design's surge requirements.