The Siemens SIRIUS 3RB2035-2QB0 is a solid-state overload relay — CLASS 20E trip curve, rated for main circuit voltages up to 690 V AC-3. It mounts directly to a contactor, so it integrates into the same DIN-rail footprint as the contactor assembly. The front face is IP00 (open), meaning it lives inside a panel; the ATEX Ex II (2) GD certification allows installation in Zone 2 gas or Zone 22 dust hazardous areas when paired with an appropriate enclosure.
CLASS 20E means the relay allows the motor to draw locked-rotor current for up to 20 seconds before tripping. If your motor has a harder start (high inertia load), you'd step up to CLASS 30; for a soft-start or VFD-fed motor, CLASS 10 or 10E is more common. This part sits in the middle of the range.
Main circuit terminals are screw-type, accepting solid conductors 0.5 to 4 mm² (or 2x 0.5 to 2.5 mm²) and stranded up to 35 mm² (2x 25 mm²). AWG equivalents: 2 x max 4 AWG stranded, 1 x 18–2 AWG solid. That covers most panel wiring up to about 25 A — no compression lugs needed, just a screwdriver.
Environmental and EMC resilience
Shock rated at 15g / 11 ms, and it's immune to 2 kV bursts on power ports and 1 kV on signal ports per IEC 61000-4-4 severity level 3. Surge withstand is 6 kV. That's solid for industrial panels near contactors or drives — you won't get nuisance faults from switching transients.