JPH0612696B2 - Double induction current heating tube - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to a double induction current heating tube. The main use of the product of the present invention is to prevent snow melting or freezing near rails or rail points.

[Prior Art] As a heat source for heating for preventing snow melting or freezing near a rail or a rail point, hot water, hot air, hot oil, or antifreeze circulation has hitherto been attempted.

However, these heat source utilization methods have the following problems in use. That is, a. With the hot water type, there is a risk of freezing damage to the piping when it becomes impossible to circulate due to a power outage, etc. The warm air type is not economical because the energy transferred per unit volume is small and The oil or antifreeze type had a problem of environmental pollution (pollution) at the time of liquid leakage.

In this respect, the electrothermal type is excellent in that it does not have the above-mentioned problems, but the devices that can be used as specific heating elements are limited, and in reality, skin current heating tubes and the like were known. .

An induction skin current heating tube (hereinafter referred to as "prototype") as a kind of the heating tube is known, and is described, for example, in "Electrical Engineering Handbook" edited by The Institute of Electrical Engineers, 1978, and is widely used in the field of surface heating. The heating tube is also a "simple induction current heating tube" (hereinafter referred to as "simplified type") that is easy to manufacture and manufacture [Patent Application Publication No. 58-16,104 (March 1983).
No. 1,185,318], which is also known.

The above-mentioned heating tubes are all ferromagnetic steel tubes, but the relationship between the thickness t _{1 of the} tube and the depth S ₁ of the skin of the alternating current is different between the “prototype” and the “simplified type”. It was

That is, the former has the relationship of the following expression (1), and t ₁ > 2S ₁ (1), and the latter has the relationship of the following expression (2).

0.5S ₁ <t ₁ <2S ₁ (2) On the other hand, the configuration common to both is that the number of tubes in one set is two or multiples when the power source used is a single phase, and three when three phases are used. Alternatively, it is a multiple.

Furthermore, the "simplified", when the number of sets of heating pipe consisting of two or three is more, the thickness t ₁ of the heat generating tube (1) of t
_In order to prevent the leakage magnetic flux to the outside of the tube due to being thinner than ₁ , close and parallel pairs of adjacent heating tubes,
The condition was that both ends of the heat generating tubes in each set were electrically connected.

As is well known, the skin depth S ₁ (cm) of the alternating current according to the above equations (1) and (2) is, as well known, the resistivity of the heating steel pipe ρ (Ωcm), the relative permeability. Is μγ (-) and the frequency of the alternating current is (Hz) And S ₁ is about 0.1 cm when is the commercial frequency.

[Problems to be Solved by the Invention] As described above, the known prototype has a wall thickness t ₁ larger than that of the simple mold, as is clear from the comparison between the equations (1) and (2). Therefore, the secondary processing is difficult depending on the purpose. On the other hand, in the case of the simple type, although the wall thickness t ₁ is thin, it is necessary to closely adjoin adjacent pipes in parallel in the structure of the wiring of the insulated wire, so that the simple type structure may not be suitable depending on the purpose of use. .

Therefore, in the present invention, the wall thickness t ₁ of the heating tube is determined by the above equation (2).
However, the present invention intends to solve the generation of the leakage voltage due to the leakage magnetic flux from the heat generating tube by means other than the simple type.

The present invention, as is clear from the title of the invention, is a double induction current heating tube, so the ferromagnetic heating tube in the relationship of the above-mentioned formula (2) is used. In order not only to closely adjoin each pair of heat generating tubes that are adjacent to each other in parallel as in the simple type, but to further ensure the prevention effect, (t ₁ + t ₂ )> (S ₁ + S ₂ ), (S ₂ ≧ S ₁ )
A metal plate having a skin depth S ₂ and a wall thickness t ₂ determined in (4) surrounds the entire circumference of the heating tube. At this time, the number of constituent heating tubes is not limited to two (in the case of a single phase) or three (in the case of three phases), and may be an integral multiple of those depending on the position, shape or heating purpose of the object to be heated. By setting the above, the degree of heating can be adjusted. The grounds for deriving the formula (4) are as follows. That is, the journal of the Denkihoku Kyokai; "Denen" No. 25, January 1986, SECT method (1), pages 6, 7 and 11, 12 and Gihodo; published April 15, 1965, published by Electrodynamics Basic (Section 7-03) pp. 157-162 Analogy was made from plated conductors.

To further illustrate, t ₂ when the upper limit t ₁ 2S ₁ of t ₁ from was S ₂ ≧ S ₁ when shown with reference the above equation (2) Equation (4) at the upper and lower limits of rewriting t _1> ( When S ₂ −S ₁ ) ≧ 0 t ₂ lower limit t ₁ 0.5S ₁ t ₂ > (S ₂ +0.5
S ₁ ).

At this time, the upper limit of t ₂ is t ₂ > 2S ₂ by analogy with the above equation (1), and it goes without saying that it will be about t ₂ 2S ₂ unless there are special circumstances.

[Object of the Invention] As apparent from the above, an object of the present invention is to provide a double induction current heating tube capable of adapting the constituent tube group and the outer peripheral metal plate according to the heating purpose. Another object of the present invention is to provide a heat generating tube in which leakage magnetic flux can be easily prevented and a metal plate on the outer periphery can have touch resistance.

[Means for solving problems]

The present invention has the following main constitution (1) and embodiment constitution (2).

(1) In a induction steel heating tube composed of a ferromagnetic steel tube having a wall thickness of t ₁ and a skin depth of an alternating current of S ₁ , and an insulated wire inserted in the tube, the t ₁ is 0.5S. ₁ <t ₁ <2S ₁ (2), even number if the alternating current power source for energizing the induction heating tube of the ferromagnetic steel tube is a single phase, 3 if it is three phases
1 or multiples thereof are parallel to each other and have both ends aligned to form an integral tube group, and the tube groups are electrically connected to each other at the both ends and inserted into each ferromagnetic steel tube. Or two or more insulated wires are connected so as to form one series wire for each phase for the entire tube group, the insulated wire is a primary circuit, and the ferromagnetic tube is a secondary wire for the AC power source. In addition, the thickness of the outer circumference of the ferromagnetic steel tube group in the longitudinal direction is t
Surrounding with a metal plate of ₂ , the thickness t ₂ of the plate and the depth S ₂ of the skin of the alternating current are (t ₁ + t ₂ )> (S ₁ + S ₂ ), (S ₂ ≧ S ₁ ).
A double induction current heating tube characterized by being determined from equations (2) and (4) so that (4).

(2) The two parts according to the above (1), wherein a part of the periphery of the outer peripheral metal plate having a wall thickness of t ₂ is composed of the metal surface to be mounted of the plate to which the double induction current heating tube is mounted. Heavy induction current heating tube.

Prior to describing the present invention with the following embodiments, a prototype induction skin current heating tube and a simplified induction skin current heating tube will be described with reference to the drawings.

FIG. 3 is a schematic cross-sectional view for explaining the simplest prototype and simple model in the case where the power source is single-phase alternating current and FIG. 4 is three-phase alternating current.

In Fig. 3, 1 and 2 are a pair of ferromagnetic steel pipes, and both ends of them are
They are electrically connected by 7 and 8, and a single circuit is formed by the single-phase AC power source 4 and the insulated electric wire 3 penetrating the steel pipes 1 and 2, and a current 5 flows. On the other hand, since the steel pipes 1 and 2 are connected by 7 and 8, a secondary circuit is formed and a current 6 flows.

In such a circuit, if the steel pipe 1,
If the wall thickness of 2 has the relationship of the above-mentioned formula (1), the magnitudes of the primary current and the secondary current are almost equal, and since these currents have opposite flow directions, the leakage flux to the outside of the tube Is not generated, and the secondary current almost flows into the depth S ₁ of the inner skin of the heat generating tube to generate heat and does not flow to the outer surface of the tube, so it can be used as a safe heating element. did it.

On the other hand, in the simplified type, the wall thickness t ₁ and the depth S ₁ are determined by the above formula (2).
Therefore, the primary current 5 (hereinafter referred to as i ₁ ) and the secondary current 6 are
(Hereinafter, i ₂ ) are not equal to each other, so that a leakage magnetic flux is generated in the space outside the steel pipes 1 and 2, and a voltage having opposite directions appears on the outer surfaces of the steel pipes 1 and 2. This voltage is
Could be reduced by closely
Since it does not become completely zero over the entire circumference of the steel pipe,
The total length of the steel pipes 1 and 2 was also limited.

The above is a description of the prototype and simple induction heating tubes.

Next, FIG. 4 shows the case where the power source has three phases and the primary circuit thereof is connected in a star shape. In the figure, 9, 10, 11
Is a heat generating tube made of a ferromagnetic steel tube, 12, 13, 14
Forms a primary circuit with insulated wires, one of which is the terminal of the three-phase power supply 15 and the other is a star-shaped connection by the connection 22,
Primary currents 23, 24, and 25 flow, respectively.

The heating tubes 9, 10, 11 are connected 16, 17, 18, 1.
Since it is connected as one body with 9, 20, 21 etc., a secondary circuit is formed and currents 26, 27, 28 are made to flow, but
Depending on whether the condition (1) or (2) is met, it becomes a prototype or a simplified model, and the same precautions as in the case of the single-phase circuit in FIG. 3 are required.

FIG. 5 shows that, while FIG. 3 shows a pair of two ferromagnetic heating tubes 1 and 2, forming a secondary circuit, another pair of ferromagnetic heating tubes 1 ′ and 2 is provided separately. ′, Both ends of which are 1, 2
In the same manner as 7 and 8 of the above-mentioned set 7, a secondary circuit is formed by being electrically connected by 7'and 8 ', and the insulated wire 3 penetrates these two sets in series to form a primary circuit with the power supply 4. Is shown. The number of secondary circuit sets formed by these sets of ferromagnetic heating tubes can be increased to a larger number as needed.
Needless to say, the same can be applied to the case of three phases in the figure.

An embodiment of the present invention will be described based on the above description of the known art.

FIG. 1 is a schematic view for explaining the double induction current heating tube 34 of the present invention. In the figure, 1 and 2 are the ferromagnetic heat generating tubes shown in FIG. 1 or FIG. 3, and their cross sections are shown by solid lines. In the figure, 12 pieces are one set,
Illustration of an insulated wire that serves as a primary circuit is omitted. Three
Reference numerals 2 and 33 are electrical connections at both ends of the heat generating tube group, and specifically may be welded as shown in the drawing.

Reference numeral 31 is a heat transfer plate between a metal plate 29 described later and a rail (not shown). In the present invention, the respective wall thicknesses t ₁ of the twelve heat generating tubes are configured to have the relationship of the above equation (2), but even if these heat generating tubes are brought into close contact with each other as shown in the figure,
Regardless of the closeness, the leakage magnetic flux does not disappear in all of the outer circumference of the heating tube group, that is, in the circumferential direction.

Therefore, in the present invention, the outer circumference of the heating tube group consisting of these 12 tubes is surrounded by the metal plate 29. And its wall thickness t
₂ is given by the above equation (4). Further, the metal plate 29 is made of a ferromagnetic steel material, and it is desirable to completely surround the outer circumference of the heat generating tube to form a magnetically closed circuit, but even if it is not necessarily completely wound up, a closed circuit is finally formed. I wish I could.

For example, since the railroad rail which is one of the objects of use of the present invention is a ferromagnetic material, it is possible to substitute a part of the metal plate 29, that is, a portion corresponding to the heat transfer plate 31, with this rail. is there. In such a case, it is desirable to consider that the magnetic circuit is as complete as possible by the contact between the metal plate 29 and the rail.

In FIG. 1, reference numeral 30 is a terminal box for supplying power to the individual heat generating tubes 1, 2 and the like inserted into the double induction current heat generating tube 34 of the present invention, and the spaces 35, 36 are the heat generating tubes 1, 36. It is for passing an insulated electric wire through 2nd grade. Space 35, 36
Although the lids on both sides are not shown in the figure, such a lid is not so necessary to prevent the magnetic flux leakage of the heating tube of the present invention. If the length of the metal plate 29 in the portion forming the spaces 35 and 36 is sufficient, it helps to prevent the leakage magnetic flux at the above-mentioned wire and the ends of the heating tubes 1 and 2.

FIG. 2 is intended to show that not only one insulated wire can be passed through the heating pipes 1, 2 etc., but also a plurality of insulated wires can be run in series with each other. Three insulated wires are passed through.

Other numbers have the same meanings as in FIG.

[Operation] The present invention, unlike the induction skin current heating tube that is the prototype, prevents leakage flux outside the heating tube by the heating tube itself, or, like the induction current heating tube that is a simple type, uses a single-phase In the case of two parallel three phases, in the case of three phases, it is not intended to prevent the generation of leakage magnetic flux to the outside of the heat generating tube only by closely contacting the three heat generating tubes, and the metal plate 29 of FIG. The feature is that the role of preventing magnetic flux leakage to the outside of the plate is shared.

Of course, in the case of the present invention, the metal plate 29 has an eddy current based on the leakage magnetic flux, which causes the metal plate to generate heat. On the basis of the secondary current flowing in the heating tube and in the insulated wire carrying the primary current.

(Effect of the Invention) According to the present invention, since a thin-walled heating tube can be used in place of a large-walled heating tube, not only the manufacturing and processing of the product of the present invention can be facilitated but also the entire The weight can be reduced and the magnetic flux leakage can be prevented by utilizing the metal plate 29 surrounding the heat generating tube. Further, the heating tube and the metal plate can be made of different materials.

This means that, for example, the heating pipe is a normal steel pipe, and the metal plate 29
By using a steel material to which a small amount of chrome is added, corrosion resistance can be provided without impairing its magnetism, and as a result, the economical efficiency of the product of the present invention can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory view of a double induction current heating tube of the present invention, and FIG.
The figure is an explanatory view showing a method of passing an insulated wire to the heating tube,
3 and 4 are schematic sectional views showing the principle of a single-phase or three-phase induction skin current heating tube which is the basis of the present invention, and FIG. 5 shows two sets of single-phase induction current heating tubes. It is a cross-sectional schematic diagram showing being connected to one alternating current power supply. In these figures, the numbers represent: 1, 2, 9, 10: Ferromagnetic steel tube 3, 12, 13, 14: Insulated wire to make a primary circuit 4, 15: AC power supply 7, 8, 16, 17, 18, 19, 20, 21: Heat generation Electrical connection of steel pipes 22: Star-shaped connection points 32, 33: Electrical connection at both ends of heating tube group 5 (or i ₁ ), 23, 24, 25: Primary current 6 (or i ₂ ), 26, 27, 28: Secondary current 29: Metal plate 30: Power supply terminal box 31: Heat transfer plate 34: Double induction current heating tube 35, 36: Space portion 37: Insulated wire

Claims (2)

[Claims] _1. A ferromagnetic steel tube having a wall thickness of t ₁ and a skin depth of an alternating current of S ₁ and an induction current heating tube comprising an insulated wire inserted in the tube, wherein t ₁ is 0. .5S ₁ <t ₁ <2S ₁ (2), and if the alternating current power supply for energizing the induction heating tube of the ferromagnetic steel tube is a single phase, an even number, and if it is 3 phases, 3
1 or multiples thereof are parallel to each other and have both ends aligned to form an integral tube group, and the tube groups are electrically connected to each other at the both ends and inserted into each ferromagnetic steel tube. Or more insulated wires are connected so as to form one series wire for each phase for the entire tube group, the insulated wire is a primary circuit, and the ferromagnetic tube is a secondary wire with respect to the AC power source. as a circuit, further, the outer periphery of the direction of the length of the steel pipe group surrounds a metal plate thickness is t _2, and a depth S ₂ of the skin of the thickness t ₂ and alternating current of the plate (T ₁ + t ₂ )> (S ₁ + S ₂ ), (S ₂ ≧ S ₁ ) ...
A double induction current heating tube characterized by being determined from equations (2) and (4) so that (4). _{2. The} outer peripheral metal plate having a wall thickness of t ₂ and a part of the periphery of the outer peripheral metal plate is composed of an attached metal surface of an attached body to which a double induction current heating tube is attached. Double induction current heating tube according to paragraph.