Reliable? Durable? A true all-rounder? Say hi to PTC! - Heating with temperature-dependent resistors
Whether cartridge heaters, convection heaters, or contact heaters: PTC stands for self-regulating heating technology on the spot. PTC heating elements bring gas mixtures, liquids, air, or solids to a preset temperature while regulating themselves. They feature high operational safety and do not overheat nor catch fire. These robust all-rounders are a safe choice even for demanding applications, such as automotive or high-voltage applications.
How does heating with temperature-dependent resistors work?
Physical functioning and advantages of heating solutions with PTC Thermistors
What exactly is PTC heating technology? What does a ceramic have to do with heating? And what is a PTC resistor? When researching the topic of "heating with positive temperature coefficient", one stumbles across quite a few keywords: Heating resistor, heating ceramic, or PTC thermistor. We take a closer look at this thing called PTC and explain what it’s all about.
Due to its unique composition, the PTC resistor is an electronic component made of ceramic (barium titanate), featuring a positive temperature coefficient (=PTC). Therefore, the current always flows particularly well when the temperature is low. This is where the name "PTC thermistor" comes from. However, if the temperature rises, the resistance of the PTC increases, and less current flows. Why is that so?
PTC ceramics are composed of tiny crystals through which the electric current flows. However, if the temperature rises, so-called barrier layers form at the boundaries of these crystals. These disrupt the movement of the electrons, making it more difficult for the current to flow.
In other words, a PTC heating element works best whenever the heat dissipates particularly well. If not, its natural resistance increases, and the self-regulation sets in. This is not a bad thing, but rather a desirable safety feature! This particular physical behavior is called “PTC effect”. It makes PTC heating technology a process-safe solution for a wide range of applications.
Temperature-dependent resistors in the role as heating element
Their fast and homogeneous heating is just one of the many benefits of PTC heating elements. Compared to traditional heating solutions with resistance wire, PTC offers many advantages. But what can you expect from a PTC heating element in the field? How does it behave in the application, and what should you pay attention to?
Typical behavior of a PTC ceramic heater
The typical resistance curve of a semiconductor as a function of temperature is called the “PTC Curve”. The initial resistance of the PTC decreases somewhat with increasing temperature until the lowest resistance value Rmin is reached.
The PTC warms up quickly thanks to this low resistance in a cold state, thus featuring a short heat-up time.
Another unique feature is the inrush current peak. Since the PTC shows its lowest resistance at Rmin, a considerable amount of current flows at this point. Every time the heater is switched on, an increased inrush current can be expected for a few seconds.
Now, the actual PTC behavior begins, and the resistance increases nonlinearly up to the nominal temperature Tc. From this point, also known as the Curie temperature, the resistance increases sharply by several powers of ten.
The operating range of the PTC extends from the nominal temperature Tc to the maximum final temperature Te, where hardly any current flows. The maximum temperature of a PTC depends on the composition of the ceramic and can be determined in advance. Once the PTC has reached this temperature, it is in a state of equilibrium between electrical and thermal energy. If the heat dissipation is improved, the PTC ceramic cools down. The associated reduction in resistance causes the electrical power to increase until a new state of equilibrium is reached.
Advantages of a PTC heating solution
No matter what shape the final heating solution - contact heating elements, air duct heaters, or interior heaters - they all come with the benefits of PTC heating technology:
Durable heating ceramics with good heat retention and low abrasion
High electrical conductivity of the material at low temperatures
Pre-contacted with electrodes for safety and operational integrity
High thermal output per surface area allows for strong heat on the spot
Can be used without a thermostat, no controls necessary
Integrated overheating protection thanks to the PTC effect
High operational safety
Energy-efficient; hardly any current flows at high temperatures
Heating elements adapt dynamically to the ambient temperature
Features high-voltage insulation, no additional grounding required
Can be flexibly applied to realize heating solutions for a wide range of installation spaces
The PTC resistor, a true all-rounder in the field of electric heating! What are you waiting for??