JPH0526316B2 - - Google Patents

Abstract

Elongate electrical devices, comprising two conductors with electrical elements connected in parallel between them, have improved performance if the power supply is connected to one conductor at the near end and to the other conuuctor at the far end. Particularly useful devices are heaters, e.g. PTC conductive polymer heaters. The power supply is connected to the far end of the device through a connection means whose electrical properties can be correlated with those of the device in order to obtain a wide range of useful results. For example the connection means can have PTC, NTC or ZTC character and can be a simple conductor or another elongate device. The power supply can be DC or single-phase, two-phase or three-phase AC. A circuit of the invention is shown in Figure 3.

Description

[Detailed description of the invention]

The present invention relates to elongated electrical devices, in particular heaters and electrical circuits with heaters. Many long electric heaters, such as those used in the chemical industry for heating pipes, tanks, and other equipment, have two (or more) relatively low-resistance heaters connected to one end of the power supply and operating the entire length of the heater. Equipped with a conductor. Between these conductors,
A plurality of heating elements are connected in parallel with each other.
The advantage of such a heater is that it can be cut to length if required. In the first type of heater described above, the heating element is a continuous or segmented conductive polymer located between a plurality of conductors. For many users, it is preferred that the elongated heater be self-adjusting. This can be achieved by using a continuous strip of conductive polymer, at least in part exhibiting PTC properties. Although the elongated heater conductors described above have relatively low resistance, there is still a net potential loss between the two conductors as the distance from the power supply increases. And since the amount of heat generated by the heating element depends in part on the potential difference between both conductors,
The above losses limit the usable heater length. The maximum usable length of such a heater can be increased by increasing the shape of the conductor, but this method is expensive, makes the heater heavier and reduces its flexibility. Another limitation of self-regulating heaters is that at low temperatures the resistance of the heaters is often much lower than their resistance under steady state operating conditions. That is, a very large current flows through the heater the first time the heater is switched on, resulting in current inflow problems. Another limitation of many heaters is that they can only be operated with a supply voltage within a certain range. Several types of thin heaters and the conductive polymers used in the heaters described above are described in U.S. Patent Application No. 2952761, 2978665, 3243753, 3351882;
3571777, 3757086, 3793716, 3823217, 3858144,
3861029, 4017715, 4072848, 4085086, 4117312,
4177376, 4177446, 4188276, 4237441, 4242573,
4246468, 4250400, 4255698, 4272471, 4314230,
4315237, 4318881, 4330704, 4334351 and
4361799, published magazine Polymer Science 19 No. 812~
815 pages (by Clason and Kubert); Magazine Polymer Engineering and Science No. 18, 649~
653 pages (1978, by Narkis et al.); West German Patent Application No. 2634992; 2755077; 2746602;
2755076; and 2821799; existing European patent applications No. 0038713, 0038714, 0038715, 0038718,
0063440 and 0067679. According to the findings of the present inventor,
The performance of a long electric heater with two long electrical conductors and multiple PTC electrical elements can be substantially improved. Connect the power supply to the first power supply at one end of the device.
A plurality of PTC electrical elements are connected in parallel between the two conductors by connecting one of the electrical conductors and connecting the heater device to the second conductor at the other end of the device. . The present invention provides a circuit configuration that can uniformly heat the circuit without causing current flow problems even in a very long circuit. According to this invention
Three similar heaters, including PTC conductive polymer heater elements, are combined and balanced with a three-phase power supply. In one aspect of the present invention, a three-phase power supply φ
1, φ2, φ3 and a neutral point N, and three long self-regulating heaters connected to the power source, (A) each heater is substantially the same, and (B) each heater is ( a) having a proximal end and a distal end located at opposite ends of the heater, the proximal end being closer to the power source 8 than the distal end; (b)(i) having a proximal end and a distal end, the proximal end (ii) is provided adjacent to the first metal conductor and has a near end and a far end, the near end being closer to the power source 8 than the far end; (iii) one continuous strip of PTC conductive polymer 11, with the first and second metal conductors 1, 2 close to each other;
a plurality of PTC electric heating elements connected in parallel with each other between; (C) each heater being part of a composite heating device; (a) a long self-regulating heater; (b) a proximal end and and a far end, and the near end is connected to the power source 8 from the far end.
(c) having a near end and a far end, the near end being closer to the power source 8 than the far end;
(d) having a near end and a far end, the near end being more connected to the power source 8 than the far end;
(e) an electrically insulating jacket 41 surrounding the heater, third, fourth and fifth metal conductors, each conductor being insulated from the entire length of each composite heating device; (D) three combined heating devices are end-to-end, and the first combined heating device is closest to the power source, the third combined heating device is furthest from the power source, and the second combined heating device is located between them. (B) The proximal end of the first metal conductor 1 of the first heater is connected to the power source 8.
(F) The near end of the first metal conductor 1 of the second heater is connected to the far end of the third metal conductor of the first composite heating device, and the (G) the proximal end of the first metal conductor 1 of the third heater is connected to the far end of the third metal conductor of the second composite heating device; The proximal end of the third metal conductor of the second composite heating device is connected to the far end of the fourth metal conductor of the first composite heating device, and the proximal end of the fourth metal conductor of the first composite heating device is connected to the fourth metal conductor of the first composite heating device. (H) The far end of the second metal conductor 2 of the first heater is connected to the near end of the fourth metal conductor of the second composite heating device, and the fourth metal conductor of the second composite heating device is connected to the fourth metal conductor of the second composite heating device. A far end of the conductor is connected to a proximal end of a fourth metal conductor of the third composite heating device, and a distal end of the fourth metal conductor of the third composite heating device is connected to a far end of the second metal conductor of the third heater. (I) The far end of the second metal conductor of the second heater is connected to the proximal end of the third metal conductor of the third composite heating device, and the far end of the third metal conductor of the third composite heating device is connected to the third metal conductor of the third composite heating device. (J) the proximal end of the fifth metal conductor of the first composite heating device is connected to the neutral point N of the power source 8; (L) the distal end of the fifth metal conductor of the second composite heating device is connected to the proximal end of the fifth metal conductor of the second composite heating device; (M) the distal end of the fifth metal conductor of the third composite heating device is connected to the proximal end of the metal conductor (a);
connected to the far end of the second metal conductor of the third heater, (b) the far end of the third metal conductor of the third composite heating device, and (c) the far end of the fourth metal conductor of the third composite heating device; An electric circuit is provided. Another invention of the present invention provides a heating device used in the first invention, and still another invention provides an assembly suitable for constituting the first invention. For simplicity and clarity in the description and claims of the present invention, the terms "near end" and "distal end" are used herein to include a plurality of elongated conductors and used to represent the end of a device. However, improvements may be made such that, for example, within a loop, the "far end" is closer to the power supply than the "near end," or the near and far ends are equidistant from the power supply. It will be understood that devices are also encompassed by the invention. For simplicity and clarity in the description of the present invention, the term "elongated self-regulating electric heater" is used herein to refer to a long self-regulating electric heater having (a) a proximal end and a distal end located at opposite ends of the heater; (b)(i) a first elongated metal conductor 1 having a proximal end and a distal end; (ii) disposed adjacent to the first metal conductor and having a proximal end and a distal end; , a second long metal conductor 2; (iii) one continuous strip of PTC conductive polymer 11, the first and second metal conductors 1, 2;
a plurality of PTC electric heating elements connected in parallel with each other between; The various electrical conductors may be composed of the same or different materials, such as circular metal wires (solid or stranded) or flat metal strips, and are sometimes referred to herein simply as conductors. Are listed. Generally, in a long parallel device (or devices), (a) the first and second conductors are identical to each other; (b) each conductor has substantially the same cross-sectional shape throughout the device; (c) the resistance of the conductors is as low as possible consistent with other factors such as weight, flexibility and cost; and (d) each conductor is at a constant distance from the other conductors (they are For example, it may be linear or spiral. As mentioned above, according to the unique features of the present invention:
Power can be distributed over longer circuits. Since the PTC electric heater elements c are connected in parallel to each other between the first and second conductors, normally they are equal to each other, but this is not necessary. Applicable
The PTC element may be constructed of conductive polymer or ceramic. The PTC element itself can be a single heating element; optionally
The PTC element can have a heating element consisting of a ZTC resistor connected in series with it. The form of a PTC element is, for example, a continuous piece of conductive polymer.
The at least one element may be composed of a conductive polymer, such as a strip or a web or a plurality of sections of conductive polymer. The composition of the conductive polymer element may be uniform throughout or may vary locally. Suitable conductive polymer elements include elements with PTC conductive polymer elements such that the device is a self-regulating heater, i.e. an element constructed essentially of a single PTC conductive polymer, or a single ZTC configuration. at least one surrounding element and one of e.g. a long conductor
and an element with a PTC component. FIG. 3 is a cross-sectional view of a composite heating device of the present invention, in which one PTC conductive polymer heater 10 having a polymeric insulating jacket is used.
1 and three wire conductors 111, 112, 113, each having a polymeric insulating jacket, are physically coupled by a jacket 41 made of a polymeric insulating material. The PTC conductive polymer heater 101 comprises a first long metal conductor 1 and a second long metal conductor 2, both of which are electrically connected to a strip of conductive polymer element. , in FIG. 3, it is embedded in a strip of conductive polymer 11. Neither of the metal conductors 1 and 2 is provided with an insulating layer covering the metal core. Third long metal conductor 111, fourth long metal conductor 112, and fifth long metal conductor 113
are each covered with an electrically insulating layer. These three metal conductors 111, 112, 113 are
Although it is not part of the PTC conductive polymer heater 101, it is part of the composite heating device. Said heater 101, third, fourth and fifth metal conductors 111, 112 and 113 comprising first and second long metal conductors 1 and 2 embedded in a conductive polymer.
are electrically insulated from each other over the entire length of the composite heating device and physically connected by a jacket 41 of polymeric insulating material. Embodiments The present invention will be explained with reference to several embodiments to be described later, including improved effects when both ends of the heater are driven by a single-phase power source and improvements when driven by a 3-phase power source. It has been shown to be effective. In these examples, the power supply is for 120V AC;
The heater was a self-regulating conductive polymer strip heater bearing the trademark 10PTV1 and available under license from Raychem Corporation. The heater contains carbon black dispersed in a luminescent cross-linked poly(vinylidene-based fluoride).
A pair of standard 18 AWG copper electrode wires fixed within a strip of PTC conductive polymer and surface plated with tin were provided. The heater had a power consumption of approximately 9 watts/foot under steady state conditions. The heater was subsequently cut into sections having lengths of 10, 150, 10, 150, and 10 feet. A plurality of small resistors with known resistance values are simply
Used to connect different parts of electrode wire. In these examples, the voltage drop across each of these resistors was measured and the current inflow in different parts of the connection means was calculated from the results. In Examples 1 and 2, 170 feet from the tip of the heater
(the rest of the heater was not joined); in Example 3, the entire 330 foot heater was used. In Example 1, since this is a comparative example not according to the present invention, it was connected to the power supply in a conventional manner (as shown in FIG. 1). In Examples 2 and 3, the heaters (as shown in Figure 2) were connected to the power supply in a manner according to the invention and consisted of standard 18 AWG insulated wire with tin surface plating fixed to the heaters. Third
A means of connection was used. In each embodiment, the heater and the third connecting means have a diameter of about 9° C. with water circulating therein by means of adhesive tape.
It was fixed to a single 2 inch steel pipe and then covered with a 1 inch thick insulation. The apparatus of Example 3 is shown schematically in FIG. 4, in which the 10-foot long heater segment closest to the power supply is designated Fragment 1 and is 160 feet away from Fragment 1. The 10-foot-long heater segment is designated segment 2, and the 10-foot-long heater segment furthest from the power supply is designated segment 3. The apparatus used in Example 2 is shown in FIG. However, the third
It is not shown that the electrical wires are connected to the ends of the segment 2. The results obtained from the above examples are summarized in the table below. This table includes inflow factors (i.e.
the current (in amps) in each carrier line (electrode) of each segment 1, 2 and 3; ; the voltage drop (in volts) between both carrier lines in each segment 1, 2 and 3; (a) the carrier line of the heater; (b) the conductive polymer element in the heater; (c) the third and (d) the power consumption (in watts/foot) for each fragment 1, 2 and 3 over the entire fragment. From the various characteristics obtained from the table below, it can be seen that the examples described above were made to obtain a qualitative rather than a quantitative evaluation of the advantages of the present invention. Therefore, the aforementioned relationships between those different characteristics should not be unduly relied upon. However, those features clearly show that by connecting the power supply to the far end of the heater via a third connection means, a reduction in incoming current and an equal power distribution over the entire length of the heater can be achieved. , and a reduction in the voltage drop across the conductive polymer strip.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 comprises conductors 1 and 2 fixed within a conductive polymer strip 11 and a power supply 8.
FIG. 2 is a schematic diagram showing three conductive polymer PTC heaters connected to a three-phase power supply to form the circuit of the present invention. FIG. 3 is a cross-sectional view of a composite device suitable for use in FIG. 2; FIG. 4 is a top view of a test circuit used in the example. 1, 2... Conductor, 8... Power supply device, 11... Conductive poly strip heater, 111, 112, 113...
...Wire conductor, 101...PTC conductive polymer heater.

Claims (1)

[Claims] 1. A three-phase power source φ1, φ2, φ3, a neutral point N, and three long self-adjusting heaters connected to the power source, (A) Each heater is substantially the same. (B) each heater has (a) a proximal end and a distal end located at opposite ends of the heater, the proximal end being closer to the power source 8 than the distal end; and (b) (i) a proximal end. (ii) a first elongated metal conductor 1 having a proximal end and a distal end, the proximal end being closer to the power source 8 than the distal end; (iii) a continuous strip of PTC conductive polymer 11, the proximal end of which is closer to the power source 8 than the distal end; ,2
a plurality of PTC electric heating elements connected in parallel with each other between; (C) each heater being part of a composite heating device; (a) a long self-regulating heater; (b) a proximal end and and a far end, and the near end is connected to the power source 8 from the far end.
(c) having a near end and a far end, the near end being closer to the power source 8 than the far end;
(d) having a near end and a far end, the near end being more connected to the power source 8 than the far end;
(e) an electrically insulating jacket 41 surrounding the heater, third, fourth and fifth metal conductors, each conductor being insulated from the entire length of each composite heating device; (D) three combined heating devices are end-to-end, and the first combined heating device is closest to the power source, the third combined heating device is furthest from the power source, and the second combined heating device is located between them. (E) The proximal end of the first metal conductor 1 of the first heater is connected to the power source 8.
(F) The near end of the first metal conductor 1 of the second heater is connected to the far end of the third metal conductor of the first composite heating device, and the (G) the proximal end of the first metal conductor 1 of the third heater is connected to the far end of the third metal conductor of the second composite heating device; The proximal end of the third metal conductor of the second composite heating device is connected to the far end of the fourth metal conductor of the first composite heating device, and the proximal end of the fourth metal conductor of the first composite heating device is connected to the fourth metal conductor of the first composite heating device. (H) The far end of the second metal conductor 2 of the first heater is connected to the near end of the fourth metal conductor of the second composite heating device, and the fourth metal conductor of the second composite heating device is connected to the fourth metal conductor of the second composite heating device. A far end of the conductor is connected to a proximal end of a fourth metal conductor of the third composite heating device, and a distal end of the fourth metal conductor of the third composite heating device is connected to a far end of the second metal conductor of the third heater. (I) The far end of the second metal conductor of the second heater is connected to the proximal end of the third metal conductor of the third composite heating device, and the far end of the third metal conductor of the third composite heating device is connected to the third metal conductor of the third composite heating device. (J) the proximal end of the fifth metal conductor of the first composite heating device is connected to the neutral point N of the power source 8; (L) the distal end of the fifth metal conductor of the second composite heating device is connected to the proximal end of the fifth metal conductor of the second composite heating device; (M) the distal end of the fifth metal conductor of the third composite heating device is connected to the proximal end of the metal conductor (a);
connected to the far end of the second metal conductor of the third heater, (b) the far end of the third metal conductor of the third composite heating device, and (c) the far end of the fourth metal conductor of the third composite heating device; An electrical circuit characterized by: 2. The circuit of claim 1, wherein each heater has first and second conductors embedded in a strip of PTC conductive polymer. 3. An elongated composite electric heating device comprising: (A) an elongated self-regulating heater; (a) having a proximal end and a distal end located at opposite ends of the heater; (ii) a second elongated metal conductor 2 disposed adjacent to the first metal conductor and having a proximal end and a distal end; (iii) having one continuous strip made of PTC conductive polymer 11 and having first and second metal conductors 1 and 2;
a plurality of PTC electric heating elements connected in parallel with each other between; (B) a third elongated metal conductor having a proximal end and a distal end;
11; (C) a fourth elongated metal conductor 1 having a proximal end and a distal end;
(D) a fifth elongated metal conductor 1 having a proximal end and a distal end;
13; and (E) an electrically insulating jacket 41 surrounding the heater and third, fourth, and fifth metal conductors, each conductor being insulated from the entire length of each composite heating device. Device. 4. A heater assembly comprising a three-phase power source φ1, φ2, φ3, a neutral point N, and three long self-adjusting heaters connected to the power source, wherein: (A) each heater is substantially and (a) having a proximal end and a distal end located at opposite ends of the heater; (b)(i) having a proximal end and a distal end; a first elongate metal conductor 1; (ii) a second elongate metal conductor 2 disposed adjacent to the first metal conductor and having a proximal end and a distal end; and (iii) a PTC conductive polymer. 11, the first and second metal conductors 1, 2
a third elongated metal conductor 111 having (X1) a near end and a far end, and (X2) a near end and a far end; (X3) a fifth long metal conductor 113 having a near end and a far end; (X4) a heater, third, fourth, and fifth metal conductors; an electrically insulating jacket 41 surrounding the conductors, each conductor being insulated from the entire length of each composite heating device; (C) The third composite heating device is located closest to the power supply, the third composite heating device is furthest from the power source, and the second composite heating device is located between the two; The end is power supply 8
(D) The proximal end of the first metal conductor 1 of the second heater can be connected to the far end of the third metal conductor of the first composite heating device, and the first (E) the proximal end of the first metal conductor 1 of the third heater is arranged to be connected to the second phase of the power supply 8; a third metal conductor of the second composite heating device and a proximal end of a third metal conductor of the second composite heating device connected to a far end of a fourth metal conductor of the first composite heating device; The near end of the metal conductor is prepared to be connected to the first phase φ1 of the power source 8, and (F) the far end of the second metal conductor 2 of the first heater is arranged near the fourth metal conductor of the second composite heating device. and the distal end of the fourth metal conductor of the second composite heating device is connected to the proximal end of the fourth metal conductor of the third composite heating device, and the distal end of the fourth metal conductor of the third composite heating device (G) the distal end of the second metal conductor of the second heater is connected to the proximal end of the third metal conductor of the third composite heating device; (H) a fifth metal of the first composite heating device; and (H) a fifth metal of the first composite heating device; (I) the distal end of the fifth metal conductor of the first composite heating device is arranged to be connected to the neutral point N of the power source 8; (J) the distal end of the fifth metal conductor of the second composite heating device is arranged to be connected to the proximal end of the fifth metal conductor of the third composite heating device; K) The far end of the fifth metal conductor of the third composite heating device is (a)
connected to the far end of the second metal conductor of the third heater, (b) the far end of the third metal conductor of the third composite heating device, and (c) the far end of the fourth metal conductor of the third composite heating device; An electric heater assembly comprising: