Self-regulating cable

Self-regulating cable - it is an element of a heating system, a custom once and for all when production at a certain temperature, which is maintained along the length of the automatic proleganiya mode.

Application and design a self-regulating cable

Self-regulating cable maintains the temperature regardless of ambient conditions. A distinctive feature of the recognized fact that some parts of the work on their own, independently of the other parts of the system.

The self-regulating current-carrying cable conductors are separated from the copper matrix resin. The thickness of the conductive material interspersed with particles of graphite, iron filings and the like substances. The heated matrix expands, the conductive bridges are torn. As a result, increases resistance portion, the current is decreased, the amount of heat decreases. Cooling leads to the opposite process:

• The base polymer matrix is ​​compressed.
• Electrical connections between the conductive particles becomes greater.
• The resistance between the current-carrying conductor portion is reduced.
• Electric current is increased.

According to the law Joule, dissipated power depends directly proportional to the current strength and resistance. We see for example - the first decrease, a second increase. The logic is that the electric current included in the formula in the second degree, and the resistance - only in the first. According to Ohm's law for subcircuit, both parameters are linearly connected through coefficient - the mains voltage.

It turns out that the current has a much greater impact on the allocated capacity. This is the physical principle of operation of self-regulating cable. A matrix is ​​adjusted by polymer selection, the correct dosage of fragmented conductive substance and electrical resistance. As a result, the system is carried Warm floor located under a cabinet or near the battery will consume less energy. Lying near the front door, on the threshold - more.

For mentioned quality self-regulating cable is so popular. It is enough to choose the right product at the store, and do not worry about the design and routing of the heating system. System breakdown easily monitored by any conventional method. The main disadvantage of self-regulating cable becomes price. Every housewife knows that the old cover for banks under the spin becomes invalid, if the rubber rassyhaetsya. A similar process is subject any polymer (due to the yellowing which is often seen okonechnikov plastic window sills and other frame retains its previous color).

So, in this class of products is becoming an important type of polymer and how the designers managed to block the process of disintegration of the material over the years. Prevent the degradation of today is not possible. As a consequence, the main factor limiting the performance capabilities of cables becomes depolymerization process units polyatomic molecules.

History of the concept

The text about the heating cable noted that the idea of ​​self-regulating system for the first time demonstrated the patent US2494589 A. The presentation was carried out simply, this review will be a logical addition to the above. The invention is a self-regulating cable ancestor, appeared in Norway during the Second World War.

Attacked Nazi Germany in the spring, the country was under the yoke of the invaders until the surrender of Hitler in May 1945. The Government of Norway has emigrated and has failed to have a serious impact on the course of events. Only 10% of the population supported the Nazis.

In comparison with the Scandinavian Peninsula Eastern European countries got rid of the invaders easily. For example, in Norway is constantly passed the anti-Hitler demonstrations repressed in a peaceful manner: shot only individual organizers. The military forces of the country acted as a part of the British Army, the territory of neutral Sweden, became a place of activity organized by the Norwegian police force.

In these circumstances it was born the predecessor of self-regulating cable. Under number 747 883 in Oslo on September 16, 1940 published patent authored by Peder Gunnar Sletnera. The text submitted to the Bureau before the outbreak of hostilities, and had the approval of the period of occupation. Now I understand why the inventor has staked out its own offspring in the US a couple of years after the reign of peace. May 14, 1947 Peder gave the text to the American Bureau. More than two years are news closely examined by the Commission and 17 January 1950 the patent published under number US2494589 A.

The original cable Sletnera

In the course of the text Peder Gunnar Sletner patented structure of two or more conductive electrical current bipolar (phase and neutral) conductors, isolated from each other and united n-number of parallel nnym included (see. parallel and serial connection conductors) resistors. Not a word is said about the main components of the current self-regulatory systems - the polymer matrix. Chemistry at the start of the second half of the XX century did not know how to create such complicated things. Sletner offers us resistive cable, but with the difference that the product may cut into portions of any length. This is considered a novelty:

1. The system becomes more powerful, the current-carrying conductors are taken copper and permitted any small resistance value. Consequently, the heating intensity is set during any of the production cycle.
2. Sletnera cable shows improved resiliency. During the combustion of a single resistor system operates without changes. Damage to one of the supply disables only lived section disposed to breakage location.

As a result, planning space heating systems much easier. From the text it is clear that the inventor has suggested the possibility of the use of new items for the three-phase networks. Moreover, any combination of conductors. The power dissipated in the resistors, is calculated according to the applied voltage between the current-carrying conductors (220, 380 and so forth.) According to the law Joule.

Important! Cable authorship Gunnar Peder Sletnera not recognized self-regulating in the conventional sense. Bus power combined fixed resistors, power does not change. It lacks an element that ensures a constant temperature.

For patents Sletnera followed by others. For example, U.S. 3757086 and 4037083. They each power bus wrapped resistive wire (nichrome, fechral) to increase the power density. But the system is unregulated. The first attempts to automate the maintenance of temperature in the visible filed November 19, 1979 patent US4250400 A. The main differences are:

1. Coiled segment of high-resistance wire wound around the two supply conductors, is divided in half in the middle of the thermistor body in the form of tablets.
2. Large disk sensor is physically pushed out of the cable limits. Under these purposes is provided in the insulation space, which is required to bring into contact with a controlled area (e.g., a pipe with the cold water in the deicing system).
3. As the temperature increases, the thermistor resistance increases, which decreases linearly flowing electric current. Power decreases with the square of.

The resistance of the thermistor to determine the most energy is released, the sensor resistance is comparable to the high-resistance portion of the wire. From the above pattern (taken directly from the text of the patent) that enhance heat transfer to the thermistor is taken relatively massive. It anticipates its melting during the operation of the cable. Figure given in profile, only feeding lived visible. In fact, two of them, and lie side by side along the length of the product.

The polymer matrix appear a decade later. In the text of the patent US5122641 A actively discussed something called conductive composite material based on a polymer. Readers can easily be convinced that the authors claim a two-wire system, where the lines are separated by a polymer matrix with conductivity, depending on the ambient temperature. Nothing is said about the actual polymer except for the approval of the applicability of "various materials". The filler is offered in graphite or charcoal chips.

To demonstrate prepared two samples based on polyolefins and fluoroelastomer (e.g., TEFZEL 280 and TEFZEL HT 2010) with additives of oxides of zinc, titanium, calcium carbonate. The difference in filler concentration of coal. Sample A - 7.5% by weight of filler, sample B - 11.

Cables with limitation of the operating temperature

A little earlier described inventions were variants of patents relating to the topic of self-regulating cables. The essence of the use properties of the Curie point of the second kind, where the resistance of the material changes dramatically. For example, US4117312 A patent chance considering the use of semiconductor materials based on barium titanate with lanthanum introduction of impurities to achieve the desired and unusual properties:

• Sample sizes substance 7h3h1,5 mm at 25 degrees centigrade exhibits resistance 300 ohms;
• former semiconductor at a temperature of 80 degrees Celsius shows an increase in resistance of two orders of magnitude (30 ohms).

The Curie point of said second kind for material stored in an area of ​​75 degrees Celsius. The described product is fundamentally different from those that use thermistors, dramatically reducing heat after reaching the threshold temperature. This mode is suitable for de-icing systems, where it is often difficult for the entire length of the site to maintain the desired temperature. But it is necessary to create a material with a Curie temperature near zero degrees as the difficulty is solved at once.

Using thermostats for anti-icing system otherwise unenforceable for obvious reasons. Control drainage or physically impossible porch area. Self-regulating cable or cable with an operating temperature of constraints facing the perfect solution for these cases.

In addition to other patents discussed known similar kind. Their number may tend to remove from the list after the text cited against. The patent is easy to find through any search engine on the Internet. Among the interesting notes EP0476637 A1. The idea is original because of the presence of curious thermostat. They use the Curie point of the second kind, but in relation to the properties of ferromagnetic materials.

Each relay includes a resilient contact. Upon reaching a predetermined temperature value the magnetic properties of the materials abruptly fall, and the electrical connection is broken instantaneously. It is understood that a large portion of the resistance is assumed to avoid arcing. Otherwise, the system will quickly lose efficiency. The presence of such vulnerable moving parts becomes the main limitation of the system.