What the ratings mean for the protection decision
The 1.5KE250C-E3/54: The 202V reverse standoff voltage (VRWM) is the maximum DC or AC peak voltage the TVS can sit across without conducting — a 170VAC RMS line or a 202VDC bus stays within the safe window. The 225V minimum breakdown voltage ensures the device does not start clamping during normal operation, while the 360V clamp limits the voltage seen by the protected load during a surge. The 4.2A peak pulse current at the clamp voltage tells you the surge current the device can absorb — useful for sizing the trace width and the upstream fuse coordination. The bidirectional configuration (single device clamps both polarities) saves board space compared to back-to-back unidirectional diodes on an AC line.
Sourcing an obsolete TransZorb for a legacy BOM
Vishay has marked the 1.5KE250C-/54 as obsolete. For a production line or a repair that depends on this exact order code, the supply path runs through independent distribution — surplus and new-old-stock lots are the available channel.