What the 1500W rating means for your board
The 1.5KE170-E3/73: That 1500W rating is the device's ability to absorb a transient without failing — it is not a continuous dissipation figure. For a 244V clamp voltage, the peak current works out to 6.1A, which is the current the diode shunts during the surge event. The reverse standoff voltage is 138V, meaning the diode stays off below that rail voltage and only starts conducting when the transient pushes past the 153V minimum breakdown. This part is not intended for power line protection — the spec explicitly flags Power Line Protection as No.
Obsolete — sourcing the 1.5KE170-E3/73 today
Vishay has marked the 1.5KE170-/73 as Obsolete. The part is sourced to order against an RFQ.
DO-201AA axial — board-fit and thermal note
The 1.5KE170-/73 comes in a DO-201AA (DO-27) axial-lead package, through-hole mount. The junction operates from -55°C to 175°C, which covers industrial and most automotive under-hood environments. The 1500W peak pulse rating assumes the leads are soldered into a board with adequate copper area to sink the transient heat — a free-air or minimal-pad installation derates the surge capability.