Obsolete status and sourcing reality
The 1.5KE51C-E3/54: The 1.5KE51C-/54 is officially marked Obsolete by Vishay General Semiconductor - Diodes Division, meaning the manufacturer no longer produces this part. For BOM lines that still require this exact order code, supply is through independent surplus and broker channels.
Key protection ratings and what they mean
The bidirectional single-channel design clamps both polarities with one device. Reverse standoff voltage is 41.3 V typical; the device starts conducting at breakdown (minimum 45.9 V) and clamps the transient to a maximum of 73.5 V at 20.4 A peak pulse current. That clamping voltage is what the downstream circuitry must survive.
Package and board integration
Housed in a DO-201AA (DO-27) axial-lead package — a through-hole form factor that suits point-to-point wiring or PCB mounting with the leads formed to the hole pitch. The 1.5KE package code is the supplier device designation.