What the 90 A rating means for the BOM line
The Siemens 3RF3090-1AA45 is a 1-pole SIRIUS 3RF30 solid-state relay in the 45 mm wide housing, rated 90 A continuous at load voltages from 48 to 600 V AC. That 90 A is the continuous resistive rating — for motor loads or other inductive circuits, you'll want to check the inrush and derate accordingly, but the 1200 V blocking voltage gives good headroom on 400 V or 480 V lines. Control side accepts 4-30 V DC, so it plays with standard 24 V DC PLC outputs without extra interface relays. Screw terminals keep wiring straightforward on the panel.
Package dimensions 62 x 47 x 74 mm (L x W x H). Single-pole configuration means one controlled phase per unit; for three-phase loads you stack three units side by side. Screw terminals accept up to the conductor sizes typical for 90 A circuits.