1.5 kW Zener TVS for general-purpose transient clamping
The 1.5KE27A-E3/51: Its 23.1 V reverse standoff voltage and 37.5 V clamping ceiling at 40 A peak pulse current make it a fit for 24 VDC rail protection in industrial control, power supplies, and telecom equipment — the clamping voltage sits comfortably below the typical 40 V abs-max of downstream DC-DC converters. Housed in a DO-201AA (DO-27) axial-lead package, it mounts through-hole on a PCB or terminal block — the axial body is common in point-of-use clamping where a radial or SMD part would need a separate heatsink pad.
Voltage ratings and clamping behaviour
Three voltage thresholds define the protection window: reverse standoff at 23.1 V (the DC bus it rides on without conducting), breakdown at 25.7 V minimum (where avalanche starts), and clamping at 37.5 V maximum (the voltage the load sees during a surge). A 24 V nominal rail with 10 % tolerance sits at 26.4 V — above the standoff but below the breakdown knee, so the diode stays off during normal ripple and only clamps on transients. The 40 A peak pulse current rating (10/1000 µs) is the surge capacity at the clamping voltage — multiply 40 A × 37.5 V to get the 1500 W peak power the device absorbs without failing. For shorter pulses (8/20 µs waveform) the peak current capability is higher, but the datasheet's 10/1000 µs rating is the conservative design-in number.
Obsolete — sourcing through independent channels
For new designs, a functionally equivalent TVS in the same 1.5 kW, 24 V class from Vishay or a competitor (e.g., Littlefuse, Bourns) would require a pin-for-pin comparison of the DO-201AA footprint and the clamping voltage window — no direct drop-in replacement is documented here.