DE1993603U - ELECTRIC RESISTANT BODY. - Google Patents

Description

Patent attorney RA. 3 3 O 45 "4 * " I G. 68

-ing. G. Weinhausen

Munich ß2 Munich, June 7th. 1968

48 ^M 3W * W / size

Tel es 51 es

Metro finance establishment in Vaduz / Liechtenstein

Electrical resistance body

The utility model concerns an electrical resistance body, one in the form of electrically conductive particles ^ in.einem insulating carrier material (e.g. plastic) has embedded electrical resistance material (e.g. carbon), whereby the thermal expansion coefficient of the carrier material is greater than that of the resistance substance. The invention relates in particular to a sheet resistor for heating purposes that consists of carbon in powder form, e.g. graphite or soot, consists of a resistance material, which is embedded in an electrically non-conductive or only very little conductive carrier material, e.g. plastic, is embedded and which, without regulation by a thermostat, automatically consumes its power when the temperature rises reduced and thus supplies less heat »

According to the innovation, the electrical resistance body of the type mentioned is characterized in that the dielectric. tric loss factor t, tang <f of the carrier material used

for the operating frequency at least in the temperature range between the intended end temperature of the carrier material and the beginning softening of which decreases or at least remains the same with increasing temperature.

'A resistance has already been described in which the electrically non-conductive, the electrically conductive particles of the resistance material enveloping carrier material a higher has thermal expansion coefficient than the resistance material. As a result, the electrical conductive particles, which are in a more or less good electrical contact with each other, further and further apart removed, the number of contact points decreasing what leads to an increase in the ohmic resistance. The current flow in such a resistor material would have to be in a certain, adjustable temperature range can be almost interrupted by the choice of composition. According to the equations for the thermal expansion would have to be assumed that the increase in ohmic resistance is almost directly related to the rise in temperature is proportional.

In fact, this assumption is made for sheet resistors made of the same resistor material (carbon) but different from one another Carrier substances (plastics) confirmed at low temperatures. In higher temperature ranges, such as, B, at the desired switch-off temperatures, but the increase in the ohmic resistance is much lower and thus the heat production higher than expected. From this it must be concluded that for the total heat development not just the joules "see heat that

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when a real power line arises * what matters is »but that heat is also developed in other ways *,

This additional warmth «* and that was not previously known or recognized »is created as follows:

When using alternating current, the alternating electrical fields in the insulating carrier material (plastic) generate constant polarization of the elementary particles * This is associated with energy conversion into heat. These amounts, which are noticeable even at moderate frequencies, are called dielectric losses. Their size depends not only on the frequency f ^ of the capacitance C _{1 of} the arrangement and the voltage U at the electrodes, but also on the loss factor tang 0 , where O is the so-called loss angle,.

The size of the losses P _{y is} calculated from the formula: P _v = 2Hf, CU ² . feang /

Tang / and also the dielectric constant A> (which is also decisive for the size of the capacitance G) are dependent both on the frequency, which in the present case is specified by the Metz frequency, and on the temperature substances in question have a size tang / steep from a certain temperature. Although only a small amount of Joule * heat can be generated in the resistance material when it is heated due to the interruption of the current paths, further conversion of electrical energy into heat is still possible for the reasons described above, if

the carrier material surrounding the conductive particles in this temperature range has a high dielectric constant and a has a large dielectric loss factor tang ti. In each Resistance materialj that act in the already known way should "must therefore inevitably have both the described ^ and also the effect shown here work at the same time,

The resistor body according to the present utility model is now based on the idea _s to effect a regulated heat generation without thermostat thereby to achieve safe ^ that when the resistance material (comprising Z ₀ B ₆ of plastics as unipolar built in preference "as polyolefins ^ eg". Poly Propylene, polyethylene, polybutylene or a mixture of such embedded powdery carbon) ₄ which has a positive temperature coefficient of electrical resistance, the carrier material according to its properties as a dielectric, namely according to the temperature-dependent quantities t and tang J j , is selected. The dielectric loss tangent (! • tango) of this support material, for "B _# ^ plastic should ent" not in the intended for heat generation Temperaturbe *. rich (e.g. ". 20" 60 ° G) be greater, that is, contribute to the Joule * see heat development, than - beyond this range (e.g. "above 60 ° C), in which a decrease in heat generation leads to self-regulation of the Temperature is desired as a safeguard against overheating of the resistance material and thus melting of the plastic, or it should remain in the intended heating range and no progressive increase or a maximum in the range of the desired heating power with increasing temperature

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reduction (e.g., between 70 and 100 ° C ^ when the enamel " temperature of the plastic is between 80 «* 100 ° G) show« Plastics of the first kind are 'zj3, various polyethylene' types, plastics of the latter type are ζ .B * some PVC «* types,

These requirements are met by ζ, B _# certain silicone varnishes and silicone chewing stains, as well as polyhalogen hydrogen such as polytetrafluoroethylene «Because especially at higher temperatures * at which the direct current paths are partially interrupted *, the capacitive resistance could otherwise play a greater role in the current consumption than the ohmic resistance «,

Because of the embedding material _s example in the production of Fläehenheizleitern small layer thickness ,, in many ways be "sondere claims made must (eg, B _e good mechanical properties, high softening) can and these may not be combined with the required properties as a dielectric - * The following possibility is offered as a way out:

By choosing one that envelops the conductive particles Insulating material with a floorboard that is particularly favorable for these purposes » tric properties and lower melting point than the Trä * » a moderate increase in its dielectric properties. loss factor when the temperature increases in the critical range between the desired maximum temperature and the beginning of the softening of the resistance material can be approximately compensated by Offset the conductive pigment to be embedded in the plastic with a dielectrically loss-free cable insulation oil and good

Homogenization at a slightly higher temperature for better Penetration "so that the conductive particles are as similar as possible" be moderately wetted with it.

This electrical resistance material described can now either be "self-supporting" without further additives or armor « calendered to increase the mechanical stabilization to the film or to the film or another suitable Shape to be extruded «

However, this resistance material can also be applied to an electrically non-conductive "carrier material (such as * paper, aesthetic paper or tight ** or wide-meshed fabrics made of plastics" such as Diolen, Trevira etc "or asbestos or fiberglass) to increase its mechanical strength , e.g. by calendering ,, lamination ^ impregnation, by dipping or spraying ,, provided it is a liquefied resistance material in the form of a lacquer, a dispersion in a liquid phase or a melt of the embedding material ^ in which the actual resistance material _Λ the carbon particles. remain homogeneously distributed.

The drawing shows "an example of the execution of a ■: Resistance body according to the utility model, namely it shows a resistance film in plan, ■ of which - only part of the outside * surface is indicated in its appearance or shown in the manner of a parish »

The resistor body 1 is made of non-conductive carrier "material 2 _t for example, a plastic film whose dielectric

■ - ■■■■ ■. ■■ -: - f \

Loss rate decreases or at least remains constant at elevated temperature and until it begins to soften »In this The carrier material is powdered carbon, e.g. * graphite or soot, embedded in fine particles 3 * These carbon particles can be equipped with insulating material before embedding, e.g. to be soaked in insulating oil »

Claims (1)

8th " S chut talks 1 _# electrical resistance body _ψ - especially layer ** resistance for heating purposes, which has an electrical resistance material (e.g. * carbon) embedded in the form of electrically conductive particles in an insulating carrier material (e.g. * carbon) ^ where the thermal expansion coefficient of the carrier » material is greater than that of the resistance material, because ** is characterized by the fact that the dielectric loss factor £. · tang / of the carrier material used for the operating frequency is at least in the temperature range between the intended end temperature of the carrier material and its beginning softening with increasing Temperature decreases or at least remains the same. 2 »Electrical resistance body according to claim 1 _s characterized in that the dielectric loss figure £, * tang </ of one or more» the resistance material enveloping _{J (together} with this insulation material introduced into the carrier material e _$ , which has a lower softening point than the carrier material travel, at least in the temperature range between the anticipated final temperature of the carrier material and its beginning softening decreases or at least remains the same with increasing temperature, 3 * electrical resistance body according to claim 2, characterized in that the dielectric loss coefficient C- * tang / of the carrier material and / or of the or the resistance « Insulation material enveloping it in the temperature range of the heating-up period increases and before reaching the intended end « temperature decreases again. k _% Electrical resistance body according to claim Z _3, characterized in that the dielectric loss coefficient ^ * tang <7 of the carrier material shows an increasing weak increase with increasing temperature, the insulating materials surrounding the resistance material in the temperature range between the intended end temperature and Beginning of softening of the resistance «the dielectric loss coefficient of the stand material decreases or at least remains constant» r-. «« Cn «,;, -« * e _W ; c ;, _(e "'jJ- ^ JtZX ^ in ff fT' ^ *" ^A ™ <* ™ 9 «-. ^ rechHlco« -nwraw « gebunr «^ classified who ^ A ^ AiS Z ° J ^ ^"'^ ^1eÄWßi ZX ^ in ff fT "the usual price" aefefwt ^Ö "" *? ^Föen "'" ^ ^ouc "" fofopj ",. Öä, R _{m .