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About PTC

About PTC
PTC knowledge
Characteristic of PTC heater element
Source: | Author:Admin | Publish time: 2011-07-07 | 126 Views | Share:

What is PTC?
PTC is short for Positive Temperature Coefficient whose material is
BaTiO3. PTC heating elements are small ceramic stones with self-limiting temperature characteristics. Since it advantages in temperature-sensitive, current limiting, time delay and noise-free, it become ideal replacement in some places for traditional Ni-Cr resistance wires, with its advantages in safety, long life and self-regulation.


The dynamic resistance and output of PTC heaters makes them an excellent choice for providing controlled electrical heat. In many applications it is possible to do away entirely with thermostatic controls. Simplification of design and reduced energy consumption represent significant cost savings for a given application. The removal of failure prone components such as thermostats can also add significantly to the reliability of a product. Safety is an added benefit, since no matter how much current is applied to the PTC thermistor; it will never surpass its intended surface temperature.

1. Resistance-Time

The R-T chart below describes main characters of PTCR. R-T stands for the relations between zero resistance and temperature of PTC thermistor. Initially, resistance falls when temperature goes up (NTC character). Later on, it would soar up when it reaches desired temperature. At last, when it passes the MAX Resistance Value, the resistance would return to NTC status

Resistance vs Time
Tc Curie Temperature:
Tmax Max temperature:
Tp Max work temperature:
Tmin Min Temperature:
T25 standard room temperature 25
RC switch resistance:
Rmax Max resistance:
Rp Max working resistance:
Rmin Min resistance:
R25 Resistance under standard room temperature:

2. CurrentTime

current vs  time

Resistance  vs time

Initial resistance of PTC heating element is small and inrush current is high when wired to powe

r, with temperature going up, the current will reach the top, as resistance goes up, current will go down and be stable.

2. Stable Power

For same PTC heater, its stable power will change with change of radiation condition. Better radiation will give PTC higher power. Also thickness of PTC thermistor is also key factor of its power, if PTC pellet is thin; it has better heat conductivity and has higher power. Power of same PTC thermistor with better radiation will be dozens of time more than that with lower radiation. Also PTC pellet with higher Curie temperature will have higher power.

Power  vs time

4.Balance of heat and radiation

It refers to stable power of PTC heater. The following is diagram of influences.