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Thermal Fuses

ATC Semitec stock SEFUSE thermal fuses which offer thermal protection for rechargeable batteries, electric motors, transformers, heating elements and small electrical appliances.  One-shot thermal fuses are defined by their temperature setting and also by their current rating, the maximum continuous current that can be applied.  We also supply PEPI bimetal thermal fuses which offer ultimate high temperature protection up to 280°C.

What is a Thermal Fuse?

A thermal fuse (or thermal cut-off or “tco”) is a one-shot, non-resettable, temperature-sensitive device that provides ultimate temperature protection in small appliances and electronic circuits.  Thermal fuses cannot be reset or repaired, they have to be replaced once the original fault that caused them to open has been rectified.

Thermal fuses are fail-safe devices which activate when other safety measures fail to operate, therefore preventing temperatures rising to dangerous levels, and will help to prevent fires. This could either be due to malfunction or misuse

Thermal fuses therefore offer the ultimate thermal protection. For single use that cannot be reset or repaired. They have to be replaced once the original fault that caused them to fail has been rectified. In the case of many consumer products, this would mean replacing the appliance.

Unlike circuit breakers, thermal fuses only react to excessive temperatures and not to excessive current (unless the excessive current itself it the reason for the temperature rise)

Thermal switches are sometimes used as thermal fuses, as they automatically reset itself once the temperature drops.

When would you use a thermal fuse?

Thermal fuses are generally used in heat producing electrical appliances within both household electrical appliances and industrial applications.

Specific examples include tumble dryers, hair dryers, convector heaters, coffee makers, laser printers and battery packs

When designing with a thermal fuse, you need to consider the operating current, applied voltage and the duty hours of the appliance that it will protect.  The normal running temperature needs to be a minimum of 25°C below the fuse opening temperature including any self-heating due to I²R or current self-heating. The Th (holding temperature) and Tm (maximum temperature) values stated for the fuse should also be taken into account to ensure reliable operation over the required product life.

Call us today on 01606 871680 to discuss your thermal design requirements and using our innovative suppliers and our extensive technical knowledge, we will work with you to provide the optimal solution for your products.