The 1.5SMC540A: That 1500 W figure is the product of the clamping voltage and the peak pulse current at that test condition: at 740 V clamp the device handles 2 A of surge current before the junction temperature exceeds the safe operating area. Breakdown occurs at a minimum of 513 V, and the clamping action limits the transient to 740 V maximum. For a 480 VAC line (rectified to ~680 VDC bus), this part clamps before the bus capacitors see overvoltage — but verify the margin between your nominal rail and the 486 V standoff.
Package and board-fit — DO-214AB (SMC)
The supplier device package is listed as DO-214AB (SMCJ), so the pad layout matches JEDEC standard SMC dimensions. Power line protection is marked 'No' — this TVS is intended for signal or DC bus transient suppression, not continuous AC mains clamping. The 1500 W rating assumes a single-shot surge; repetitive events require thermal analysis of the PCB copper area under the cathode tab.
The series includes unidirectional and bidirectional variants; this is the unidirectional version with one channel.