ABB TF42-B thermal overload relays are economic electromechanical protection devices for the main circuit, complying with the latest railway rolling stock standards and allowing installation in passengers or driver cabins for trains frequently operating tunnels or undergrounds. They offer a reliable protection for motors in the event of overload or phase failure. The devices have trip class 10. The thermal overload relays are three pole relays with bimetal tripping elements. The motor current flows through the bimetal tripping elements and heats them directly and indirectly. In case of an overload (over current), the bimetal elements bent as a result of the heating. This leads to a release of the relay and a change of the contacts switching position (95-96 / 97-98). – Manual or automatic reset selectable – Phase loss sensitive acc. to IEC/EN 60947-4-1 – TEST and STOP function – Trip indication on the front – Temperature compensation – Suitable for three- and single-phase applications – designed in accordance to the applicable parts of IEC 60077 standard – shocks and vibration withstand conforming to IEC 61373 (category 1, class B) – usable according to European fire and smoke safety standard EN 45545-2