Terminologija parametrov PTC termistorja

‌Heating & Temperature Control and PTC Thermistor Parameter Terminology for Overcurrent Protection.

PTC‌ (Positive Temperature Coefficient) is a professional term, mainly referring to semiconductor materials or components with a positive temperature coefficient. The resistance value of PTC material increases significantly when the temperature rises. This characteristic makes PTC materials widely used in electronic circuits.

PTC Heaters, 200W DC 12V Heating Electric Insulated Ceramic Thermostatic High Power Small Greenhouse Heater

PTC grelni element, Aluminijasta lupina Keramična poliimidna filmska plošča, AC DC 110V 120C Termostatska orodja za ogrevanje

PTC Thermistors WMZ12A, MZ11, MZ12, MZ23, MZ6

Rated zero power resistance R25
Zero power resistance: refers to the extremely low power consumption added to the PTC thermistor when measuring the PTC thermistor value at a certain temperature, so low that the change in the resistance of the PTC thermistor caused by its power consumption can be ignored. Rated zero power resistance refers to the zero power resistance value measured under an ambient temperature of 25°C.

Minimum resistance Rmin:
Refers to the minimum zero power resistance value that a PTC thermistor can have.

Curie temperature Tc:
For the application of PTC thermistors, the temperature at which the resistance value begins to increase steeply is important, and we define it as the Curie temperature. The resistance of the PTC thermistor corresponding to the Curie temperature is RTc = 2*Rmin.

Temperature coefficient α:
The temperature coefficient of a PTC thermistor is defined as the relative change in resistance caused by temperature changes. The larger the temperature coefficient, the more sensitive the PTC thermistor is to temperature changes. α = (lgR2-lgR1)/lge(T2-T1)

Surface temperature Tsurf:
Surface temperature Tsurf refers to the temperature of the surface of the PTC thermistor when the PTC thermistor is under the specified voltage and in thermal equilibrium with the surrounding environment for a long time.

Action current Ik:
The current flowing through the PTC thermistor is sufficient to make the self-heating temperature rise of the PTC thermistor exceed the Curie temperature. Such a current is called the action current. The minimum value of the action current is called the minimum action current.

Action time ts:
Under the condition of 25℃ environment, add a starting current to the PTC thermistor (guaranteed to be the action current). The time it takes for the current passing through the PTC thermistor to drop to 50% of the starting current is the action time.

Non-action current INk:
The current flowing through the PTC thermistor is insufficient to make the self-heating temperature rise of the PTC thermistor exceed the Curie temperature. Such a current is called the non-action current. The maximum value of the non-action current is called the maximum non-action current.

Maximum current Imax:
Maximum current refers to the maximum current carrying capacity of the PTC thermistor. When the maximum current is exceeded, the PTC thermistor will fail.

Residual current Ir:
Residual current is the current in thermal equilibrium at the maximum operating voltage Vmax.

Maximum operating voltage Vmax:
Maximum operating voltage refers to the highest voltage allowed to be continuously maintained on the PTC thermistor at a specified ambient temperature. For the same product, the higher the ambient temperature, the lower the maximum operating voltage value.

Rated voltage VN:
Rated voltage is the supply voltage below the maximum operating voltage Vmax. Usually Vmax = VN + 15%

Breakdown voltage VD:
Breakdown voltage refers to the maximum voltage carrying capacity of the PTC thermistor. The PTC thermistor will fail when the breakdown voltage is above it.

Round PTC ceramic heating element for small household appliances

Square ceramic PTC thermistor heating plate for heater electric heating equipment