Solid State Devices
Polymer Type Devices
Polymer type devices are basically conductive strips of a plastic like material. They rely on heat generated from increases in temperature or current to generate thermal energy to provide a self heating effect. This results in a change of the polymer matrix increasing in resistance which then causes the device "trip" the electrical load. This device remains at an elevated temperature so it remains in a "tripped" state or until the power is removed. Normally, these can only be used in lower voltage applications and were not designed for continuous-duty applications. Although there have been improvements in their thermal sensing abilities, these devices are not as thermally sensitive as bimetallic controls. Polymer devices rely on the expansion capability of the polymer matrix and are susceptible to problems due to improper installation. Also, once these devices are exposed and function under certain fault conditions their operating characteristics may change.