Four important parts of a thermal Overload relay
1. Bimetallic strip: a temperature-sensitive metal strip that bends when heated, creating a physical mechanism for tripping the relay when overheating occurs.
2. Heater element: an electrical resistor that heats up when current passes through it, providing the heat necessary to activate the bimetallic strip.
3. Adjustable overload setting: a mechanism that allows the user to set the desired trip point for the relay based on the maximum allowable current for the protected motor or equipment.
4. Contact mechanism: a set of contacts that open and close based on the status of the bimetallic strip, disconnecting the power supply to the protected equipment when an overload condition is detected.