What it is and what it does
The Siemens SIRIUS 3RB2036-1QW1 is a 3-pole solid-state overload relay for motor protection in three-phase circuits. Its Trip Class 10E means it will trip within 10 seconds at 7.2× the current setting — the right speed for standard induction motor starts where the rotor doesn't stall. The solid-state sensing eliminates the bimetal drift you get with thermal relays, so the trip curve stays repeatable over the operating range of -25 to +60 °C. It carries ATEX Ex II (2) GD certification, meaning it can be used in Zone 1 gas and Zone 21 dust hazardous areas when paired with an appropriate motor and enclosure. That's the main differentiator from a standard thermal overload — it's spec'd into Ex-rated panels from the start.
Key ratings and what they mean for fit
The Trip Class 10E is the headline rating: it defines the thermal memory curve for motor starting. If your motor accelerates in under 10 seconds, this class matches. For longer starts (high-inertia loads like fans or centrifuges), you'd need a Class 20 or 30 relay — but that's a different order code. The auxiliary contact block provides 1 NC contact and 0 CO contacts. That NC is wired into the contactor coil circuit to drop the motor on overload. No spare CO for a remote signal unless you add an auxiliary contact block externally. Wire termination is screw-type on the control side, accepting solid conductors from 0.5 to 4 mm² (or 2× 0.5 to 2.5 mm²). The main current circuit uses straight-through transformers — the motor leads pass through the relay's integral current transformers, so no separate CTs are needed. Surge voltage resistance is rated at 6 kV, and burst immunity meets IEC 61000-4-4 severity level 3 (2 kV on power ports, 1 kV on signal ports). That's enough for most industrial panels without additional suppression. Shock resistance is 15g for 11 ms, and it can be mounted in any position. Stand-alone installation means it doesn't require a dedicated mounting base — just screw it to the panel plate or DIN rail adapter. Dimensions are 55 mm wide, 92 mm high, 109 mm deep — a compact footprint that fits alongside a 3RT2 contactor in a standard motor starter combo.
Where it's used
This relay goes into motor control centers (MCCs) and standalone starter enclosures protecting three-phase induction motors up to the current range of the straight-through transformer window. The ATEX approval makes it a natural fit for chemical, oil & gas, grain handling, and pharmaceutical lines where Ex-rated equipment is mandatory. The 100% humidity tolerance during operation means it holds up in washdown areas and outdoor cabinets without conformal coating worries.
Lifecycle and sourcing reality
RoHS compliance is confirmed with a substance prohibition date of July 1, 2006, covering the original EU RoHS directive. The reference code per IEC 81346-2 is F (protective device).