Thermal relay
Federal Elektrik

Thermal relays disables the motor via contactor in case of overload or phase cut-off ; that is, a contactor equipped with thermal relay becomes a much more useful and advantageous device. because, addition of a thermal relay to the contactor provides protection for both consumers against over current and for contactor against impacts of over heating due to over current. Federal Thermal Relays are manufactured up to 32A, as compensated against environmental temperature in accordance with TS EN 60947-4-1, IEC60947-4-1 standards and CE.

Each phase in thermal relay is connected to an over current opener. When bimetals heat up, they open the circuit by pushing the differential opening lever. In case of failure of any of the phases, only two of bimetals operate and over current opener gets into service faster than in case of overloading. Thermal relay mechanism compensates changes in environmental temperature and prevents relay from being affected by ambient temperature.

Average value of opening characteristic of thermal over current relay in hot operating condition is below the opening characteristic of the relay in cold operating condition. That is, cold relay at a particular opening current is opened approximately 1/4 later than relay in hot condition. According to IEC 60947-4-1, it is required for the relay to break the circuit in 2 minutes at the latest at 1.5 times loading in hot condition.

Average values of opening characteristic for a relay heated by adjustment current is about 10% - 30% of the opening values of the relay operated in cold condition. These values depend on limit current strength between 1.05 - 1.2 times of adjustment current.