What it is and what it does
The Siemens 3RB2046-2UB0 is a SIRIUS solid-state overload relay — a three-pole device that protects motors against overcurrent and phase imbalance by monitoring the main current circuit and tripping according to a CLASS 20E curve. CLASS 20E means the relay allows a locked-rotor current to persist for up to 20 seconds at cold start before tripping — a standard match for standard induction motors driving pumps, fans, and conveyors where the starting transient is moderate.
Mounting and integration
Fastens directly onto a contactor via the contactor-mounting method, so no DIN-rail slot is consumed — it stacks on the contactor's own body, keeping the panel width to the contactor's footprint plus 6 mm side clearance. Dimensions are 70 mm wide, 106 mm high, 124 mm deep. Mounting position is any, which simplifies layout in tight enclosures. Main circuit terminals accept screw-type connections: solid 0.5–4 mm² (2x 0.5–2.5 mm²) or stranded 2x (10–50 mm²) and single 10–70 mm². Auxiliary and control circuits use separate screw terminals.
Environmental and compliance
Rated for operation from -25 to +60 °C, storage and transport from -40 to +80 °C. Withstands 100 % relative humidity during operation and 15g / 11 ms shock. Carries ATEX type protection PTB 06 ATEX 3001 Ex II (2) GD, meaning it can be used in Zone 2 gas and Zone 22 dust atmospheres when installed in an associated enclosure. Surge voltage resistance is 8 kV; burst immunity meets IEC 61000-4-4 severity 3.
Auxiliary contact ratings
The built-in auxiliary contacts are rated for switching: 2 A at 24 V, 0.55 A at 60 V, 0.3 A at 110/125 V, 0.11 A at 220 V, and 4 A at 120 V or 3 A at 230 V. These are the maximum continuous make/break currents per contact — useful for sizing the control transformer or PLC input draw.