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About PTC
PTC (Positive Temperature Coefficient) is the acronym means that the temperature coefficient is, the great pan-corrected temperature coefficient of semiconductor materials or components. Usually we talk about the PTC is correct temperature coefficient thermistor, or PTC thermistor. PTC thermistor temperature is a typical sensitivity of the semiconductor resistor, over a certain temperature (Curie temperature), its resistance values with increasing temperature of a step higher.

PTC thermistor is a thermally sensitive semiconductor resistor. Its resistance value rises sharply with increasing temperature after a defined temperature (Curie temperature) has been exceeded. This feature makes them ideal for use in countless applications of modern electrical and electronic engineering, for example as resettable fuses against current overload or as shortcircuit protection in motors. You find special motor starter PTC thermistors in the compressors of refrigerators for instance. Thermal protection of motors and transformers is another example of the versatility of PTC thermistors. The applications extend to measurement and control engineering, to entertainment, household and automotive electronics, plus data systems and telecommunications of course. PTC thermistors are also suitable as self-regulating heating elements, in auxiliary heating, nozzle heating and carburetor preheating in automobiles, as well as in many domestic appliances such as door locks for washing machines, or glue guns and hair curlers. 

Due to the PTC thermistor is the more energy saving and safe component.it is  widely used in many  household electrical apppliances,electric power facilities and electronic products. In general,appliacation using PTC thermistor can be categorized according to three unique characteristics; resistance-temperature (R-T), current-time (I/T) and current-voltage (I/V) characteristic.

Figure 1 shows the typical dependence of the zero-power resistance on temperature.

The properties of electrically loaded PTC thermistors (in self-heated mode) are better described by the I/V characteristic than by the R/T curve (see figure 2). It illustrates the relationship between voltage and current in a thermally steady state in still air at 25 °C, unless another temperature is specified.

PTC Thermistors
Thermistors are temperature dependent resistors ant “PTC” stands for positive Temperature Coefficient of resistance. Ceramic PTC thermistor is a functional semiconductor that exhibits a highly positive temperature coefficient with the rise of tem perature hits Curie Point (Tc) initially: the resistance goes down as temperature rises.Then, its resistance increases rapidly past a refere-nce temperature (or Curie temperature) and this is what we call the “PTC domino affect”Using different temperature coefficients.we can make differernt PTC for varies heater sensitive ceramics for differern applications. Due to the PTC thermistor is the most energy saving and safe componert, it is widely uesd in many household electrical appliances , electric power facilities, and electronic produ-cts.In general, aplplicantions using PTC thermistor can be categorized according to three unique characteristics: resistance-temperat-ure(R/T), current-time(I/T)and current-voltage(I/T)characteristics.

Resistance-Temperature Characteristics

The use of A category characteristicsis suttable for thermal sensor, over-heat protectors,motot stator and high heat generation heaters. Qhereas, in the B category, those withcurie point below 120℃, the Steep slope gives a higher resistance, sensitivity in a onoff situation, making them ideal for switching purposee.g. Thermal sensors ,overcurrent protectors,delays and degaussors.

Current-Time Characteristics

Turrent for a much shortet periond of time time.The typical application ohe current Time characteristics shows the relationship between the Current and the time under the operaton in rated voltage , the higher the volgate,a higher peak cf curren t-Time characteristics PTC used in degaussor,motor stator and delays. 

Volgate-Current Characteristics

Volgate-Current characteristiscs is usually named after V-A character-istics.The V-C diagram is taken at steady state current(when current meas-ured becomes steady after some time from switched on)in still air 25℃ am-bient condition. On a standard ambient/heat dissipationo environment the PTC’s steady surface temperature(Ts) is practically the same and the power(wattage)within a small variance even if different voltages are used.This gives self-heating PTCthe advantage of dual of multi-voltage usage in different countries of different voltage.