The Siemens 3RF3025-1AA02 is a 1-pole semiconductor relay from the SIRIUS 3RF30 family, housed in a 45 mm wide package with screw terminals. It is rated for 25 A continuous current and accepts a control voltage of 24-230 V AC / 24 V DC, making it a direct replacement for electromechanical contactors in applications where silent, wear-free switching is required.
What the 25 A rating means in practice
The 25 A rating is the continuous load current the SSR can handle at its rated voltage range. For a solid-state relay, this figure governs the thermal design of the panel — the 45 mm width provides a specific surface area for heat dissipation, and the buyer should plan for adequate air circulation or a heatsink if the load approaches the full 25 A at elevated ambient temperatures. Unlike an electromechanical contactor, there is no coil to hold in; the control input draws only the leakage of the internal optocoupler and zero-crossing detection circuit.
Integration into the control panel
The control voltage range — 24-230 V AC or 24 V DC — covers the common signal levels from PLC digital outputs (24 V DC) as well as direct AC line-voltage control, so no interposing relay is needed when the control signal matches one of these levels.