Thermal Cutoffs (Thermal Fuses)

About Thermal Cutoffs (Thermal Fuses)

Thermal cutoffs are one-shot, non-resettable devices that permanently open a circuit when sensed temperature reaches a specified limit. Unlike conventional current fuses, they respond primarily to surrounding heat and provide final protection against overheating or fire. Axial, radial and surface-mount versions protect appliances, heaters, transformers, motors, power supplies, batteries and power semiconductors. They require replacement after operation and differ from cycling thermostats or resettable thermal protectors.

Select by rated functioning temperature, tolerance, holding temperature and maximum temperature, not trip temperature alone. Verify AC or DC voltage, current, breaking capacity and suitability for the actual resistive, inductive or motor load. Mount the device with reliable thermal contact while maintaining insulation distances. Check body style, lead length, mounting pressure, sealing and UL, VDE or IEC approvals. Soldering, welding, lead bending and encapsulation can damage the element; follow the manufacturer's lead-distance, heat-sinking and installation instructions, and never reuse a device that has opened.