Wholesale Bimetal Thermostat Control

The product showcased on Qianxun Electrical Technology Co., Ltd, a bimetal snap‑action thermostat designed for electric kettles and similar heating appliances, is a key component for ensuring both user safety and reliable performance. Leveraging the inherent characteristics of bimetallic strips, the thermostat exploits the differential expansion of two bonded metals under increasing temperatures. As the kettle nears a boil, steam is directed onto the curved strip. The heat causes one metal to expand slightly more than the other, triggering a sudden snap action that disconnects the circuit and cuts off power to the heating element

The snap‑action mechanism is particularly important: unlike gradual contact resistance changes, the rapid opening and closing produced by the bimetallic disc help to reduce arcing and prolong contact life. It also ensures sharp and consistent cut‑offs, preventing partial current flow that could otherwise cause overheating or failure.

A well‑engineered bimetal thermostat must balance sensitivity, life‑cycle stability, and safety compliance. As the temperature rises, the strip must snap at the set threshold with hysteresis, then reliably reset when the temperature drops. The alignment of the disc relative to an internal pusher or trigger must fall within tight tolerances. Some manufacturers use a single-component disc with an integrated “mechanical amplifier” that increases movement without added assembly complexity—an innovation introduced by early pioneers like Strix, which eventually became an industry standard.

In high‑volume production, maintaining tight tolerances is critical. Automated assembly lines align the disc, pusher, spring, and contacts accurately. Materials are chosen not only for their expansion coefficients but also for thermal conductivity, fatigue resistance, and electrical insulation. Copper or copper alloys are often used for contact surfaces to ensure low resistance and protect against oxidation.

Beyond the ordinary “boil‑dry” and boil‑cut‑off function, designs may incorporate additional fail‑safes. For example, double‑trip thermostats include one disc for steam‑triggered cut‑off and another section acting as an over‑temperature protector if normal switching fails. Some designs integrate a one-time thermal fuse to fire at a higher temperature level, offering a last-resort fail-safe when all other mechanisms have failed.

Electrical ratings are another crucial specification. Commonly rated at 13 A and 250 V AC, these thermostats align with the power draw of kettle elements. The housing and terminal insulation are engineered to sustain this demand and to prevent current leakage. Manufacturers typically test parts in an environmental chamber, cycling through dozens of on/off operations at heat and humidity levels. Standards tailored for the kettle market are applied to ensure conformity with the safety requirements of different regions.

Surface finish and physical design are also important. The exposed edges of the thermostat housing should provide precise mounting interfaces, often designed with three screw holes or clamps for installation of steam chambers. This ensures accurate positioning so that steam efficiently reaches the bimetal strip, providing consistent cut‑off performance.

Regarding materials, brass terminals with tin plating offer robust conductivity, while the housing may include bronze bushings to help pilot airflow for steam activation. Vacuum‑sealed metal chambers might be used to improve response time by reducing thermal inertia. Some high-volume manufacturers may apply nickel-plated steel discs for improved corrosion resistance, while others utilize stainless steel or brass-based discs depending on price and lifecycle targets.

On the manufacturing side, maintaining constant quality involves statistical process control. Automated optical inspection systems verify disc curvature, spring preload, and contact gap. Electrical tests at assembly completion check insulation resistance, contact resistance, and switching action at target temperatures. Aging tests expose the component to cycles well beyond typical use to test for failure modes such as contact welding or metal fatigue.