Bimetallic
Abimetallic overload relayconsists of a small heater element wired in series with the motor and abimetalstrip that can be used as a trip lever. Thebimetalstrip is made of two dissimilar metals bonded together. ... If the cause of theoverloadstill exists, therelaywill trip again and reset at given intervals.
Thermaloverload relaysare economic electromechanical protection devices for the main circuit. They offer reliable protection for motors in the event ofoverloador phase failure. The thermaloverload relaycan make up a compact starting solution together with contactors.
The simplestoverload relayis activated by heat caused from high current flowing through theoverloadand over abimetallicstrip. ... As thisbimetallicstrip heats up, one metal will expand faster than the other and cause the assembly to curve.
Overload relays protectamotorby sensing the current going to themotor. ... When current is too high for too long, heaters open therelaycontacts carrying current to the coil of the contactor. When the contacts open, the contactor coil de-energizes, which results in an interruption of the main power to themotor.