When the melting alloy is a solid, the shaft of the ratchet wheel is held from turning.

Melting Alloy

A type of thermal overload relay element that melts or deforms with excessive current, providing protection by breaking the circuit.

Ratchet Wheel

A ratchet wheel is a mechanical component consisting of a wheel or gear with teeth, designed to allow movement in one direction while preventing backward motion.

Solid

A state of matter characterized by structural rigidity and resistance to changes of shape or volume.