Thermistor motor protection relay Standard evaluation device 22.5 mm housing screw connection 2 changeover contacts US = AC/DC 24 V manual/automatic/remote RESET with ATEX approval. 2 LEDs (READY/TRIPPED) ensure safe galvanic isolation. The device features a test/RESET button, wire break monitoring, short circuit monitoring, and is safe against zero voltage.

The SIRIUS 3RN2 thermistor motor protection relay protects motors from overheating, even in explosion-prone areas, through direct temperature measurement with ATEX approval. The direct measurement of the motor winding temperature allows for the protection of a motor under unusual conditions such as heavy starting, braking operation, frequent switching, or inadequate cooling, thus avoiding unnecessary over-dimensioning of the motor.

The devices can be used in gas or dust explosion hazard areas. The use of PTC sensors means that parameterization of the devices is not necessary. LEDs allow for quick fault diagnosis. The devices are climate-resistant, touch-safe, and can be used worldwide thanks to a wide voltage range and international approvals.

Available as mono- or bistable evaluation devices, with and without ATEX approval, with one or two sensor circuits, as well as with automatic, manual, and/or remote RESET. The devices are available in screw or spring-loaded technology (Push-In). There are versions with a width of 17.5 mm or 22.5 mm, for TH35 rail mounting or for screw fastening with an adapter (accessory), as well as with hard gold-plated contacts. Uniform accessories for all device variants, such as detachable terminals, insertion tabs, and coding pins, simplify selection and inventory management.

The 3RN2 thermistor motor protection relays replace the proven 3RN1 series. SIRIUS relays - a program for all cases.