800 V off-state — the margin that matters on 480 V lines
The TPDV825RG is an STMicroelectronics Alternistor triac rated for 800 V off-state voltage and 25 A RMS on-state current. The 800 V ceiling gives real headroom on 277 VAC or 480 VAC mains where line transients can hit 600 V — a 600 V rated triac would be running at the edge. The Snubberless construction means the device commutates inductive loads (motors, solenoids, transformer primaries) without the usual RC snubber network across the main terminals, saving two passives and the board area they occupy.
Non-repetitive surge rating is 250 A at 60 Hz (230 A at 50 Hz). That number tells you the triac can survive the cold-start inrush of a motor or the charging current of a large capacitor bank without shorting. The TO-3P package (TOP-3) puts the die on a copper tab that bolts to a heatsink — the junction-to-case thermal path is the limiting factor for sustained 25 A, not the silicon itself.
No official replacement or successor order code is recorded — any cross-reference must be validated against the original application's trigger current (150 mA Igt max) and holding current (50 mA Ih max).