Thermal cutoffs and thermal protectors are nonresetting, thermally-sensitive devices that are designed to protect electrical appliances and industrial equipment from fire. They are sometimes called thermal one-shot fuses. When ambient temperature is increased to an abnormal level, the thermal cutoff senses the temperature change and breaks the electrical circuit. This is accomplished when an internal organic pellet experiences a phase change, allowing spring-activated contacts to permanently open the circuit.
Specifications
Cutoff temperature is one of the most important specifications to consider when selecting thermal cutoffs and thermal protectors. Other important considerations include:
cutoff temperature accuracy
voltage
alternating current (AC)
direct current (DC)
Features
Thermal cutoffs and thermal protectors (one-shot fuses) differ in terms of:
lead material
lead style
case style
physical parameters
Tin-plated copper wire and silver-plated copper wire are common choices for lead materials. There are two basic lead styles: axial and radial. With axial leads, the thermal fuse is designed so that one lead extends from each end of the case. With radial leads, the thermal fuse is designed so that both leads extend from only one end of the case. Cases for thermal cutoffs and thermal protectors are made from ceramics or phenolics. Ceramic materials can withstand high temperatures without degradation. At ambient temperatures, phenolics have a comparative strength of 30,000 lbs. Physical parameters for thermal cutoffs and thermal protectors include lead length, maximum case diameter, and case assembly length. Some suppliers specify an additional lead length that can be added to the specified length of the thermal cutoff or thermal protector.
Applications
Thermal cutoffs and thermal protectors are used in many consumer products and bear various marks, certifications, and approvals. Common applications include hair dryers, irons, electric motors, microwave ovens, refrigerators, hot coffee makers, dishwashers, and battery chargers.
Post time: Jan-22-2025