PPTC Fundamentals
Fuzetec Polymer PTC Technology
PPTC device and Resettable Fuse ( PTC THERMISTOR, PTC VARIABLE RESISTER, Variable Resistance PTC Thermistor, Variable Resistor, Current Limiter ) technology synergistically integrate the advance polymer material technologies, conductive material science, novel processing engineering, and fundamental electronic and electrical theory. Electrical resistance of such material and devices increases with temperature increases and vice versa. Fuzetec has successfully integrated all theses and developed a wide range of PPTC devices specifically designed to protect circuits from overcurrent.
How Does PPTC Resettable Fuse Work
FUZETEC™ resettable fuses are designed and made of patented novel PPTC material in thin chip form where conductive particles are dispersed in a polymer that has a crystalline structure. At normal operating conditions there are numerous chains forming conductive paths throughout the PPTC material. Under fault conditions (Tripped State), excessive current flows through the PPTC device and the PPTC material heats up. This makes the polymer matrix’s morphology change from crystalline to amorphous. Under these conditions the conductive particles move apart from each other, most of them no longer conduct current and the resistance of the device increases sharply. Upon fault current being removed, the resettable fuse is resetted and allows the current through the circuit again.
IH (I Hold) defined as the maximum current the device will hold at rated temperature ( 23℃) without tripping. The probability that the PPTC will trip increases as the current approaches IT (I Trip), defined as the minimum current required to cause the PPTC device to trip at rated temperature.
The range of current values between IH and IT represent a zone where performance of the device with respect to tripping can not be predicted with certainty(Fig.2, Region C). Depending on the initial resistance of the PPTC device, ambient temperature and mounting conditions, the device could either maintain a low resistance state and hold this current or it may be a sufficient current to cause the device to switch to the high resistance state.
