The 1.5KE33A-E3/51: The 45.7 V maximum clamping voltage at 32.8 A peak pulse current means a 28.2 V nominal rail sees the transient clipped to under 46 V before the diode conducts away the energy.
Parametric envelope and package fit
Breakdown voltage range starts at 31.4 V minimum, reverse standoff is 28.2 V typical — the diode stays high-impedance below the rail voltage and only clamps when the transient exceeds the breakdown threshold. Unidirectional — one channel, cathode-band polarity marked on the DO-201AA axial body; the anode connects to ground, cathode to the protected rail. Through-hole DO-201AA / DO-27 package with a -55°C to 175°C operating junction range — wide thermal margin suits PSU output stages, industrial control boards, and telecom line cards where ambient heat is high.