Automotive-grade TVS for 342 V rails
The 1.5KE400A-803E3/54: It clamps at 548 V maximum and has a 342 V reverse standoff voltage, making it a fit for protecting 300 VDC bus rails or 277 VAC rectified lines in automotive and industrial power stages.
What the 1500 W rating means for your board
At the 2.7 A peak pulse current, the diode clamps the transient to 548 V, absorbing the energy without exceeding the junction's 175°C limit. Breakdown voltage is guaranteed between 380 V (minimum) and the clamp voltage, so the diode starts conducting and shunting surge current before the protected circuit's insulation or semiconductor ratings are exceeded.
Obsolete — sourcing through surplus channels
Available through independent surplus and broker channels. No pin-compatible direct replacement from Vishay is documented — a board-level redesign to a different TVS series or package may be required for long-term supply.