What it is and what it does
The Siemens 3RB2026-1SB0-ZX95 is a SIRIUS solid-state overload relay — it protects motors from sustained overcurrent by tripping on a Class 10E curve, meaning it will open the contactor within 10 seconds at 7.2x the set current. That's the standard trip class for standard-start induction motors driving pumps, fans, and conveyors where the start time stays under 10 seconds. It mounts directly onto a contactor (contactor mounting), saving DIN rail space and keeping the power wiring short. The 45 mm width and 75 mm depth fit a standard 45 mm modular envelope — one slot in a typical panel layout. The main circuit terminals accept solid conductors from 0.5 to 4 mm², or two conductors 0.5 to 2.5 mm² each — enough for the control wiring on most motor starters up to the relay's rated voltage of 690 V AC-3.
Lifecycle and sourcing posture
The ATEX approval (PTB 06 ATEX 3001 Ex II (2) GD) means it's certified for use in potentially explosive gas and dust atmospheres — Zone 1/2 gas and Zone 21/22 dust, as a associated apparatus mounted outside the hazardous area but controlling equipment inside it. That's a compliance gate for chemical, oil & gas, and grain-handling installations.
Integration constraints
Mounting position is any orientation, which simplifies panel layout. The front face carries an IP20 rating — protected against finger contact, but not washdown; keep it inside the enclosure. Side clearance to adjacent devices is 6 mm minimum; no clearance needed above, below, forward, or backward (0 mm). Operating temperature range is -25 to +60 °C, storage and transport -40 to +80 °C. Shock rated at 15g for 11 ms — robust for machine-mounted panels on presses or conveyors. Humidity tolerance is 100% RH during operation, so condensation inside a non-condensing enclosure is fine. EMC immunity includes surge voltage withstand at 6 kV and burst transients at 2 kV on power ports, 1 kV on signal ports (severity level 3 per IEC 61000-4-4). That's the standard industrial immunity level — no special filtering needed for most factory-floor environments.
Auxiliary contact ratings — what they mean for the control circuit
The relay provides no built-in auxiliary contacts (0 auxiliary contacts). All status signaling must come from an external auxiliary contact block or the contactor's own aux. The solid-state output is rated for switching: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V, and 0.55 A at 60 V, 0.3 A at 110/125 V, 0.11 A at 220 V. These are the maximums for the internal solid-state switching element — use them to drive a PLC input or a small relay, not a contactor coil directly.