JPH1129827A - Direct electric heating device of traveling material to be heated - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device, in which it is no fear that excess current is conducted in a ground circuit even in the case of grounding a material to be heated at a position apart from a heating device, in the in-line transformer system electric heating device. SOLUTION: In the direct electric heating device, in which the material 1 to be heated continuously taveled, is passed through an iron core set in the transformer 2 and conductive roll sets 3, 4 are arranged at both sides of the transformer and electrically connected, the one side of conductive roll set 4 is grounded, and the first choke 9 wound by a coil having one turn to an iron core having an opening hole for passing through the material to be heated 1, is arranged at the opposite side of the transformer 2 to the other side of conductive roll set 3. Both end parts of the coil are connected with the one side of conductive roll set and the other side of conductive roll set, respectively and further, desirably, the second choke 11 composed of an iron core having an opening hole for passing through the material to be heated is arranged at the opposite side of the other side of conductive roll set 3 to the first choke 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for heating a material to be heated such as a steel wire or a steel sheet which is continuously running, by directly applying a current to the material for heat treatment.

[0002]

2. Description of the Related Art There are many processes for heating a continuously running material to be subjected to heat treatment such as annealing.
In addition to the very common method of heating by passing through a tunnel type heating furnace, direct current heating may be used. As shown in FIG. 6, the direct current heating causes the current-carrying rolls 32 and 33 to come into contact with at least two places on the running material 1 to be heated, and the power supply 31 is connected between the rollers, thereby causing the material 1 itself to generate heat by electric resistance. Things. Direct current heating has the advantages of significantly higher thermal efficiency than a heating furnace that relies on heat transfer to radiation and convection, the ability to heat materials very quickly, and relatively inexpensive equipment.

As mentioned above, direct energization heating can be performed in principle with at least a power source and two energization rolls, but it is not sufficient for actual equipment. That is, the voltage required for heating the material to be heated is applied between the energizing rolls, and if there is a roller or the like that grounds the material to be heated outside the energizing roll, a current flows through the ground,
Parts other than between the energizing rolls are also heated. FIG.
As shown in the above, even if the voltage is distributed by grounding the middle point of the secondary winding of the transformer of the power supply 31 and the voltage is distributed, the ground potential of the portions of the energizing rolls 32 and 33 may be a voltage of 100 V, for example. If this is not done, an electric shock will be caused even if the member comes into contact with the material to be heated far away from the electric heating device.

In order to prevent the above-mentioned problems, in actual equipment, as shown in FIG. 6, grounding rolls 35, 36 are provided outside the energizing rolls 32, 33 having a high ground potential, and the outer rolls are provided. The material to be heated is made so that the voltage of the electric heating does not reach it. In this state, a large current flows through the material 1 to be heated between the energizing rolls 32 and 33 and the grounding rolls 35 and 36. Therefore, chokes 37 and 38, that is, current limiting reactors are provided therebetween to limit the current. The choke has a magnetic path surrounding the material 1 to be heated, and is an iron core having an open window through which the material to be heated passes.

Japanese Unexamined Patent Publications Nos. 63-128125 and 1-142032 disclose another type of direct current heating apparatus for continuously running wires or strips. As shown in FIG. 7, a heated material 1 is passed through a window of an iron core of a transformer 2 provided with a winding connected to a power supply, and an energizing roll contacting the heated material on both the upstream and downstream sides of the transformer. 3 and 4, with a busbar 5 between them
These are connected by a low-resistance circuit. In this device, the material to be heated 1 itself forms the secondary coil of the transformer 2, and the electromotive force generated in the material to be heated 1 causes the current to flow through the bus bar 5 between the energizing rolls to be heated. Become. Since it can be considered that a transformer is formed in the main body of the current-carrying heating device, this is hereinafter referred to as an in-line transformer system. On the other hand, the external power supply system is used to distinguish the conventional energization heating device described above. In this in-line transformer type device, both of the energizing rolls 3 and 4 can be grounded 39 and 40, so that the necessary grounding roll is essentially unnecessary in the aforementioned external power supply type. Therefore, the equipment is simplified, and there is no danger of electric shock even when the electric roll is touched. This is a safe and excellent method.

[0006]

As described above, in the in-line transformer system, there is no problem in principle because the grounds 39 and 40 are provided at both the energizing rolls 3 and 4 as described above. In some cases, a considerable ground current 41 may be bypassed in addition to the bus bar 5 connecting between the two current-carrying rolls. This becomes remarkable when the ground resistance of each of the grounds 39 and 40 is low, for example, when a low-resistance circuit is formed through the steel frame of the building when both of the energizing rolls come into contact with the building structure. Since the busbar current itself is a large current of, for example, several thousand amperes, even if a part of the current is shunted, the current becomes considerably large, adversely affecting the life of the roll bearings, and in some cases, the bolts of the joints of the structure may be damaged. Overheating is also conceivable. Therefore, it is preferable to ground only at the position of one energizing roll, for example, the position of the energizing roll 4 on the exit side.

For this reason, for example, in FIG. 7, when only one energizing roll 4 is grounded 40, the material to be heated in the other energizing roll 3 has a low potential of about several volts, but a ground potential appears. . This is obtained by adding a voltage drop caused by a large current flowing through the bus bar to a voltage drop of the brush of the other energizing roll 3. In this case, the voltage drop of the brush is a resistance component, and the voltage drop of the bus bar is a reactance component. Since the grounding 40 of the one energizing roll 4 is normally performed at one end of the bus bar 5, the ground potential corresponding to the voltage drop of the brush of the energizing roll 4 also appears on the material to be heated in this case. Is small and can be ignored.

If the ground potential of the other energizing roll 3 is left as it is, when the material to be heated 1 is grounded with low resistance at another place on the other energizing roll side, both of the energizing rolls are connected. Busbar 5
It is conceivable that a considerable ground current flows in parallel with this current. As a countermeasure, it is conceivable to electrically insulate process equipment such as a carrier roll, a deflector roll, a pinch roll, and a winding machine that are in contact with the material to be heated upstream of the ungrounded current-carrying roll in FIG. However, the number of devices that transport or perform some processing while being in contact with the continuously heated material is usually very large. Therefore, if the measures are taken by electric insulation, the construction cost is increased and the cost of maintenance work for maintaining the insulation is also required.

In view of the above, the present invention provides an in-line transformer-type current-carrying heating apparatus as shown in FIG. 7 which has an excessively large grounding circuit even when the material to be heated is grounded at a position distant from the heating apparatus. It is an object to provide a device in which current does not flow. In particular, the electric heating device is rarely used alone, and is often provided as one device for executing a series of processes. It is preferable to design from the beginning so as not to cause any inconvenience even if it is as described above, for example, to prevent the bearings and the like from burning due to ground current. If not installed in this way, even when the equipment is first installed, the situation of the surrounding devices can be checked and no inconvenience will occur, but unexpected problems may occur when the adjacent equipment is modified at a later date. is there. In view of such a situation, the present invention provides a low-cost device that can reliably cope with any grounding situation including other devices before and after.

[0010]

As means for preventing the above-mentioned problems from occurring in the in-line transformer system, the same method as in the case of the external power supply system described with reference to FIG. A grounding roll may be provided outside the roll, and a choke may be provided between the ground roll and the energizing roll. However, in this way, even in the in-line transformer system, a grounding roll and a choke are required on one energizing roll side, and some of the advantages as compared with the external power supply system are lost. However, in the in-line transformer system, the voltage that the choke must bear is, for example, 5 V, which is much smaller than, for example, about 250 V in the case of the external power supply system, so that the iron core of the transformer is much smaller. Therefore, it is a fact that the benefit of the in-line transformer system is considerably large even if such a ground roll is required.

The present invention solves the above-mentioned problem of the ground potential which appears in the material to be heated and the problem caused by the current flowing in the process line equipment in contact with the material to be heated on the side of the current-carrying roll which is not grounded, at low cost. A continuously heated material to be heated is passed through an iron core of a transformer provided with a winding for connecting to a power supply, and energizing rolls are provided on both sides of the transformer, which are in contact with the material to be heated, respectively, and a conductive material is connected therebetween. In the direct current heating device described above, one of the current-carrying rolls is grounded, and the other of the current-carrying coils is wound on a core having a window through which the material to be heated is wound by one turn and the other of the current-carrying rolls is energized. The voltage induced on the material to be heated by the magnetic flux generated in the choke by the current flowing through the winding is provided on the opposite side of the transformer from the roll, and cancels the ground potential of the material to be heated. It is a direct resistance heating apparatus of the heated material to travel, characterized in that the ends of the windings connected to the said one current supply roll and the other conductive rolls sexual.

[0012] Further, a continuously running material to be heated is passed through an iron core of a transformer provided with a winding for connecting to a power supply, and energizing rolls are provided on both sides of the transformer, respectively, in contact with the material to be heated. In the direct current heating device in which the conductive material is connected, one of the current-carrying rolls is grounded, and one turn is wound around an iron core having a window through which the material to be heated passes. A first choke is provided on the other side of the current-carrying roll opposite to the transformer, and a voltage induced in the material to be heated by magnetic flux generated in the choke due to a current flowing through the winding cancels a ground potential of the material to be heated. The opposite ends of the winding are connected to the one energizing roll and the other energizing roll, and a second choke made of an iron core having a window through which the material to be heated penetrates is connected to the other end of the first choke. It is a direct resistance heating apparatus of the heated material to travel, characterized in that provided on the roll opposite. Further, here, the first choke and the second choke are defined as a first choke portion by providing a winding on a part of a laminated thickness of an iron core laminated in a traveling direction of a material to be penetrated and forming a remaining portion. It is also characterized in that they are integrated by making the portion of the lamination thickness of the second choke portion.

[0013]

FIG. 1 shows an example of a direct current heating apparatus according to the present invention. Reference numeral 1 denotes a continuously running material to be heated, which passes through an iron core of a transformer 2 provided with a primary winding connected to a power supply. On both the upstream and downstream sides of the transformer, there are provided energizing rolls 3 and 4 which are in contact with the material to be heated, respectively, and are connected by a bus bar 5 having a low electric resistance to constitute a direct energizing heating device. In the apparatus of the present invention, one energizing roll 4 of the energizing rolls is grounded 8, and the other side of the energizing roll 3, which is not grounded, is provided with a window through which the material 1 to be heated penetrates. A choke 6 in which a winding 7 with one turn is wound around the iron core is provided. Both ends of this winding have polarities such that the voltage induced in the material to be heated by the magnetic flux generated in the choke by the current flowing through the windings of the current-carrying roll 3 and the other current-carrying roll 4 cancels the ground potential of the material to be heated. Connect to In the following, for convenience, it is assumed that the portion of the energizing roll 4 on the downstream side, that is, the high-temperature side, is grounded, and the choke 6 is provided adjacent to the energizing roll 3 on the upstream side, that is, the low-temperature side. Irrespective of the essence of the invention, it does not matter.

With this configuration, an induced voltage that cancels the ground potential V _C of the material to be heated 1 at the position of the current-carrying roll 3 on the upstream side can be generated in a portion of the material to be heated that penetrates the choke 6. . That is, in this case, the choke 6 is excited by the current flowing through the winding 7, and a magnetic flux is generated in the choke core. Since this magnetic flux links with the heated material 1 penetrating through the choke window as well as the winding,
A voltage equal to the voltage across the winding 7 is induced in the material to be heated. As a result, the ground potential V _{C of the} material to be heated can be provided without providing a grounding roll which is necessary in the above-described prior art.
Can be offset.

The current I ₁ flowing through the winding 7 of the choke 6 is the exciting current itself of the iron core of the choke.
It will counter the ground potential V _C at. As an actual design sequence, first, the back electromotive force E at which choke should occur
[V] (effective value), and the corresponding magnetic flux Φ [W
b] can be calculated by the following equation (1), and if the design magnetic flux density B [T] is determined according to the material of the iron core, the sectional area S of the iron core
[M ² ] is obtained by the following equation (2). 2 ^1/2 E = 2πfNΦ (1) S = Φ / B (2) where f is the frequency and N is the number of turns of the coil (= 1)

On the other hand, since the magnetic path length L [m] is determined by the size of the window of the iron core through which the material to be heated penetrates, the exciting current I to obtain the design magnetic flux density B is obtained from this and the data of the magnetic permeability.
[A] (effective value) can be calculated by the following equation (3). I = L · B / (μ 0 μ r N · 2 1/2) ····· (3) However mu ₀ is the permeability of vacuum ^{(= 4π × 10 -7 [H} /
m]), μ _r is the relative permeability of the iron core

Since the choke used in the present invention can have only one winding, the exciting ampere turn itself becomes the exciting current. Therefore can not be possible to adjust the exciting current by the turns of the winding, as a general transformer design, current I ₁ of the winding 7 is designed to be considerably large value, e.g. 30A. Since the ground potential at the portion of the energizing roll in the case of the in-line transformer system is, for example, 5 V as described above, which is much lower than the value of, for example, 250 V in the case of the external power system, the choke has much less magnetic flux, in other words, An iron core with a much smaller cross-sectional area will suffice.

FIG. 2 shows an equivalent circuit of the apparatus shown in FIG. 1. The reactance 13 of the choke 6 and the impedance 14 of the line connected to the winding 7 are connected in series. The ground potential V _C is applied, and the current I ₁ flows. The voltage induced in the material to be heated 1 by the choke 6 is the same as the voltage applied to the reactance 13. That potential and the potential of the material to be heated the circuit of the windings in the inlet side of the choke 6 as described in Figure 1 is always the same V _1. Therefore reactance 13 as in FIG. 2 are represented as one, the potential of the point described in Figure 2 becomes V _1. The current I ₁ at this time is their sum when the current in the material to be heated not only circuit winding is flowing. The impedances of the lines other than those described in FIG. 2 are neglected because the distance is short. Since there is a voltage drop due to the impedance 14 of the line connected to the winding 7, the choke 6
Ground potential V ₁ of the material to be heated at a position upstream of the completely so that only the voltage remains not become zero. This voltage V ₁
Is 0.3 V when the ground potential V _{C at} the portion of the energizing roll is 5 V, for example. The impedance 14 has a small resistance, and is mostly a reactance.

In the above case, when the material 1 to be heated is grounded on the upstream side of the choke 6, a current flows between the grounding 16 of the material to be heated and the grounding 15 of the current-carrying roll as shown in FIG. I _e flows. In this case, the current is distributed depending on the ratio between the impedance of the ground circuit and the impedance of the line connected to the winding. Therefore, if the resistance of the ground circuit is relatively large, the current I
_e is not so large and there is no problem. Therefore, if the resistance of the ground circuit expected in the equipment attached to the electric heating device is not very low, the device as shown in FIG. 1 can be used.

In the apparatus shown in FIG. 1, when the resistance of the grounding circuit of the material to be heated at the upstream position thereof is low, for example, if the impedance of the line connected to the winding of the choke is the same, distribution is made on a one-to-one basis. You. As described above, the current of the winding of the choke is usually designed to have a value of, for example, 30 A. In this case, the current of the ground circuit is 15 A. Such a current may have an adverse effect on the life of the bearing, so if the equipment attached to the current-carrying heating device is complicated and if it is expected to be modified in the future, even if the ground resistance becomes low, It can be said that it is preferable to make the current of the ground circuit sufficiently low.

In the case of the current-carrying heating apparatus shown in FIG. 1, the current in the grounding circuit is limited by increasing the cross-sectional area of the iron core of the choke, but a large iron core is required to sufficiently reduce the current. For example, in FIG. 2, when the impedance of the circuit of the ground 16 is the same as the impedance 14 of the line connected to the winding of the choke, the current I _e of the ground circuit is 15 A in the above example, and is limited to 3 A. Is assumed.
As described above as an example, when the ground potential V _C of the energizing roll is 5 V and the voltage V ₁ applied to the impedance 14 of the line connected to the winding of the choke is 0.3 V, if the phase is the same, the choke is used. The back electromotive force is 4.7V. To the 3A current I _e of the ground circuit in this case, when a current of the same 3A towards windings shunts 6A, i.e. bears the potential to ground V _C at one-fifth of the current of the previous state Must. Since the voltage V ₁ of the impedance 14 across the line current I ₁ winding circuit occurs due to this the smaller is negligibly smaller, chokes is necessary to generate a counter electromotive force of 5V is ground potential V _C is there. In other words, it is necessary to generate a back electromotive force of 5 V which is larger than the previous 4.7 V by the current of 1/5, (5 V ÷
(4.7V) × 5 = 5.3 and about 5 times the iron core is required.

As described above, if the choke is designed on the assumption that the material to be heated is grounded somewhere upstream with a low grounding resistance, a considerably large choke is required.
Therefore, FIG. 3 shows an example of the direct current heating device of the present invention which solves such a problem. The configuration relating to the material 1 to be heated, the transformer 2, the current-carrying rolls 3, 4 and the bus bar 5 is the same as in the case of FIG. One of the current-carrying rolls 4 is grounded 8, and the other of the current-carrying rolls 3, which is not grounded, on the side opposite to the transformer 2, is wound around an iron core having a window through which a material 1 to be heated passes.
A first choke 9 on which the winding 10 is wound is provided. Both ends of this winding are connected to one energizing roll 3 and the other energizing roll 4 with polarities that cancel the ground potential of the material to be heated.
This first choke 9 has the same configuration and function as the choke 6 in the device shown in FIG. 1, and the design of the dimensions of the iron core can be performed in the same way. The apparatus shown in FIG. 3 further comprises a second core made of an iron core having a window through which the material to be heated 1 passes.
Is provided on the opposite side of the first choke 9 from the other energizing roll 4, that is, on the upstream side in this example.
This second choke 11 is usually provided adjacent to the first choke 9 or as integral with the first choke, as will be explained later. Unlike the first choke 9, the second choke 11 does not have a winding, and simply penetrates the material to be heated.

FIG. 4 is a diagram showing an equivalent circuit of the device of FIG. 2, the reactance 17 of the first choke 9 and the impedance 18 of the line connected to the winding 10
Are connected in series, and the ground potential V _C of the current-carrying roll 3 on the upstream side is applied to this, so that the current I ₁ flows. The voltage induced in the material 1 to be heated by the first choke 9 is the same as the voltage applied to the reactance 17, and the ground potential of the material to be heated at the upstream position of the choke 9 is V ₁ ,
The principle of the circuit, such as not being completely zero, is shown in FIG.
Is the same as In terms of the previous example ground potential V _C of the conductive rolls 3 on the upstream side is 5V, ground potential V ₁ of the material to be heated at an upstream position of the first choke 9 0.3V, winding 10
Current I ₁ flowing in the a value such 30A. In this case, when the material to be heated 1 is grounded on the upstream side of the second choke 11, as shown in FIG. 4, the grounding 16 of the material to be heated and the current-carrying roll on the downstream side via the reactance 19 of the second choke. current I ₂ flows between the ground 15 of the. This reactance 19 can to a large value more easily than the impedance 18 of the winding circuit of the first choke, becomes possible to current I ₂ of the grounding circuit to the much smaller value than the current I ₁ of the winding circuit.

Referring to the specific values of the equivalent circuit of FIG. 4 in the same manner as in the previous example, when the ground potential V _{C of the} upstream energizing roll 3 is 5 V, the value at the upstream position of the first choke 9 0.3V of ground potential V ₁ of the material to be heated is that the second choke reactance 19 voltage to be borne. Then, assuming that the current of the second choke, that is, the current I _{2 of the} ground circuit at this time is 3 A as in the above example,
This current is one tenth of 30 A of the current I1 of the _first choke. Therefore, the sectional area of the iron core of the second choke is (0.3 V ÷ 4.7 V) × 10 =
0.6 times is sufficient. In other words, even if the first and second chokes are added, a smaller core is required when the ground current is similarly limited by a single choke. Moreover, in the above example of a single choke, the calculation was made on the assumption that the impedance of the ground circuit and the impedance of the line connected to the winding of the choke were the same and the current was distributed one-to-one. If the impedance is lower than this, the current of the ground circuit further increases. On the other hand, in the device of FIG. 3, the ground current can be similarly limited without being affected by the impedance of the ground circuit.

Since the choke used in the present invention is required to have a high magnetic permeability, it is preferable to use a grain-oriented silicon steel plate as the material of the iron core. When used for electrical heating of wires and narrow strips, wound cores in the form of toroids or race tracks can be used, but large ones such as wide strips are stacked in the running direction of the material to be penetrated. It is sufficient to use a stacked iron core. When arranging the first and second chokes, separate ones may be arranged adjacent to each other. However, in the case of a laminated iron core, the installation space and labor can be reduced as an integrated one. This can be achieved by providing a winding 22 on a portion 23 of the laminated thickness of the iron core 21 as a first choke portion as shown in FIG. 5 and a portion 24 of the remaining laminated thickness as a second choke portion. good. Note that in FIG.
Reference numeral 2 denotes a terminal portion, and reference numeral 26 denotes a spacer made of iron or the like for providing a gap in the iron core by the thickness of the copper plate forming the winding.

[0026]

According to the electric heating device of the present invention, it is possible to prevent a voltage from appearing on the material to be heated outside the heating device with simple equipment without using a grounding roll. Further, when the material to be heated is grounded outside the current-carrying heating device such as another facility, the current flowing through the grounding circuit can be suppressed to an extremely small value, so that accidents such as damage to bearings can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an electric heating device according to the present invention.

FIG. 2 shows an equivalent circuit of the device of FIG.

FIG. 3 is a diagram showing an example of an electric heating device according to the present invention.

4 shows an equivalent circuit of the device of FIG.

FIG. 5 is a diagram showing an example of a choke used in the present invention.

FIG. 6 is a diagram showing a conventional energization heating device using an external power supply system.

FIG. 7 is a diagram showing a conventional in-line transformer type current-carrying heating apparatus;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heated material 2 transformer 3, 4 energizing roll 5 bus bar 6 choke 7 winding 8 ground 9 first choke 10 winding 11 second choke 13 choke reactance 14 impedance of line connected to winding 15 energization Grounding of roll 16 Grounding of material to be heated 17 Reactance of first choke 18 Impedance of line connected to winding 19 Reactance of second choke 21 Iron core 22 Winding 25 Terminal part 26 Spacer

Claims (3)

[Claims] 1. A continuously running material to be heated is passed through an iron core of a transformer provided with a winding for connecting to a power source, and energizing rolls are provided on both sides of the transformer, respectively, in contact with the material to be heated. In the direct current heating device in which the conductive material is connected, one of the current-carrying rolls is grounded, and one turn is wound around an iron core having a window through which the material to be heated passes. A choke is provided on the other side of the current-carrying roll opposite to the transformer, and a voltage induced in the material to be heated by magnetic flux generated in the choke by a current flowing through the winding has a polarity that cancels a ground potential of the material to be heated. A direct current heating device for a running material to be heated, wherein both ends of a wire are connected to the one energizing roll and the other energizing roll. 2. A continuously running material to be heated is passed through an iron core of a transformer provided with a winding for connecting to a power source, and energizing rolls are provided on both sides of the transformer, respectively, in contact with the material to be heated. In the direct current heating device in which the conductive material is connected, one of the current-carrying rolls is grounded, and one turn is wound around an iron core having a window through which the material to be heated passes. A first choke is provided on the other side of the current-carrying roll opposite to the transformer, and a voltage induced in the material to be heated by magnetic flux generated in the choke due to a current flowing through the winding cancels a ground potential of the material to be heated. Both ends of the winding are connected to the one energizing roll and the other energizing roll in polarity, and a second choke made of an iron core having a window through which the material to be heated penetrates is connected to the other of the first choke by the other energizing. Low A direct current heating device for a running material to be heated, the heating device being provided on the opposite side of the heating device. 3. The first choke and the second choke,
A winding is provided on a part of the lamination thickness of the iron core laminated in the running direction of the material to be penetrated to form a first choke part,
3. The apparatus according to claim 2, wherein the remaining lamination thickness portion is formed as a second choke portion so as to be integrated.