The Siemens 3RF3190-2AA26 is a SIRIUS 3RF31 series solid-state relay — one pole, 22.5 mm wide, built to switch resistive or light inductive loads up to 90 A continuous on a 48-600 V AC line. The control coil pulls 110-230 V AC. For motor loads or transformer primaries, you need to check the load's locked-rotor current against the relay's surge rating — the 90 A is the steady-state ceiling, not the start-up punch. This relay is designed to mount on an external cooling surface — it does not have its own integral heatsink. That means the panel builder provides a metal plate or chassis to pull the heat out. Out here in the grease, I have seen these bolted to the back panel of a control cabinet, or to a machine frame, as long as the surface is clean and flat. No heatsink in the package keeps the width tight at 22.5 mm, so you can pack several poles side by side on a DIN rail and still have room for the contactors upstream.
Termination and integration notes
Spring-loaded terminals — no screwdriver torque to worry about, but the wire strip length and ferrule size matter. Because this relay needs an external cooling surface, the mounting plate must be clean and flat — any paint or corrosion under the relay reduces thermal transfer and derates the 90 A capability. In a washdown environment, make sure the mounting surface is stainless or painted steel, not bare aluminum that will corrode.