What this TransZorb® TVS diode does on the board
The 1.5KE540-E3/54: The single unidirectional channel handles 1.94A of peak pulse current in the forward direction — sized for a 1500W surge event, not continuous conduction.
Obsolete — what that means for sourcing
For a BOM line that calls out this exact Vishay part number, the supply route is through independent distribution holding end-of-life inventory. Because the TransZorb® series covers a wide voltage range, a parametric substitute with the same 1500W DO-201AA footprint may exist at a different breakdown voltage, but no pin-compatible direct replacement under this base number is published by Vishay.
Housed in a DO-201AA (DO-27) axial-lead package, the 1.5KE540-/54 mounts through hole on a PCB or terminal block — the axial leads allow point-to-point wiring or soldering into plated through-holes on a standard 0.100-inch pitch layout. The junction temperature range spans -55°C to +175°C, covering industrial and telecom outdoor cabinet environments where ambient heat and self-heating from the surge event must stay within the silicon's thermal budget.