How Does a Thermal Circuit Breakers Work？
Thermal-Magnetic Circuit Breakers operate on two different principles. Under overload conditions, they use a bimetallic strip. Current flowing through the bimetallic strip heats it up. Excessive current causes the bimetallic strip to bend. This bending triggers the circuit breaker's tripping mechanism, initiating the first step of cutting off the power. For short circuits, the circuit breaker's electromagnetic coil activates, generating a strong magnetic field that instantly breaks the contacts. But breaking the contacts is only half the battle.
When the contacts break under load, especially during a fault, the current doesn't stop immediately. It ionizes the air, creating a high-temperature plasma channel—an electric arc. If left uncontrolled, temperatures can reach thousands of degrees Celsius, melting components, damaging equipment, and even causing a fire, thus negating the entire function of the thermal-magnetic circuit breaker. While thermal-magnetic circuit breakers are effective against overloads and short circuits, they rely on an arc-extinguishing chamber to eliminate this threat.
At the instant the contacts break, the electric arc is guided by magnetic and thermal forces into a set of precisely designed heat-resistant metal plates within the arc-extinguishing chamber. These plates are meticulously designed with optimal geometry and conductivity to provide multi-level protection. They rapidly cool the plasma, deionizing the gas; they divide a single, powerful arc into a series of smaller, weaker arcs. Most importantly, they lengthen the arc path, extending it to a critical point where the voltage required to sustain the arc exceeds the system's available voltage. The arc is then forcibly and completely extinguished. This process is not merely about cutting off the current, but also about preventing catastrophic equipment damage and protecting people from explosive arc flashes.
The performance of a thermal-magnetic circuit breaker depends entirely on the quality of its arc-extinguishing chamber. A poorly designed or manufactured arc-extinguishing chamber may fail to extinguish the arc quickly enough, leaving circuits and equipment vulnerable to damage.
At Hejing Electric (Wenzhou) Co., Ltd.,we have been dedicated to perfecting arc extinction chamber technology for decades, continuously pushing the limits of electrical protection, serving customers in the energy, manufacturing, and infrastructure sectors, and committed to sustainable development. We provide precision engineering solutions that prioritize safety, efficiency, and long lifespan. We are committed to manufacturing high-quality, highly reliable, and highly efficient Arc Chambers, providing strong support for the perfect operation of thermal-magnetic circuit breakers in various application scenarios.