JP2618299B2 - Electric heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating apparatus for electrically heating a mass-produced electrically conductive material to be heated continuously, for example, as a pre-heat treatment for galvanizing steel. The present invention relates to an electric heating device for heating.

[0002]

2. Description of the Related Art An alternating current is supplied to a material to be heated while continuously feeding the material to be heated having conductivity, for example, steel, continuously for various purposes such as preheating for plating, annealing and quenching. A device for heating a material to be heated by resistance heating is known.

As such a heating device, two sets of conductive roll electrodes sandwiching the material to be heated are provided at predetermined intervals in a feed path of the material to be heated, and the material to be heated is provided between the two sets of roll electrodes. Is known in which a ring-shaped transformer is arranged around a circle. In this device, the inside of the ring of the annular transformer is formed to be a feed passage for the material to be heated, and a primary voltage is applied from a power source to the annular transformer, so that a secondary voltage is induced in the material to be heated and the material to be heated is heated. The material is electrically heated.

In such an electric heating device, for example, a primary winding is wound over the entire length of the iron core of an annular transformer in the width direction, taps are provided at a plurality of predetermined positions of the winding, and these taps are selected. It is known that power is supplied to a primary winding via a selected tap to control heating according to the material, width, and plate thickness of a material to be heated.

[0005]

By the way, the magnetic flux density B which is an important factor in determining the specifications of the annular transformer is described.
Represents the primary voltage of the alternating current supplied to the annular transformer as E1,
If the frequency is f, the sectional area of the iron core is S, and the number of turns is n1, then B = E1 / 4.44f · n1 · S. Preventing the magnetic flux density B from being saturated is an essential condition in the design of the annular transformer.

Therefore, when the number of turns n1 is changed, for example, in order to prevent the magnetic flux density B from being saturated even when the number of turns n1 is reduced, the cross-sectional area S of the iron core is changed according to the change in the number of turns n1. Must be bigger. However, when the cross-sectional area S of the iron core is increased in this way, a large installation space for the annular transformer is required, and the installation cost is increased. In some cases, there is a problem that the annular transformer cannot be installed.

[0007] The present invention solves the above problems,
It is an object of the present invention to provide a current-carrying heating device capable of preventing saturation of magnetic flux density even when the number of turns of an annular transformer is changed and preventing an increase in installation space for the annular transformer.

[0008]

According to the present invention, there is provided an energization heating apparatus for bringing a continuously fed material to be heated into contact with a roll electrode disposed on an entrance side of a feed passage of the material to be heated.
Heating is performed by contacting a roll electrode or metal bath provided on the outlet side of the material to be heated, and an annular transformer is arranged between the inlet roll electrode and the outlet roll electrode or metal bath. The inside of the ring of the annular transformer is a passage for the material to be heated.

The product of the frequency of the alternating current supplied to the annular transformer and the number of turns of the annular transformer is set at a fixed ratio to the product of the rated frequency of the annular transformer and the minimum number of turns.

[0010]

According to the present invention, when a voltage is applied to the annular transformer, a secondary voltage is induced in the material to be heated, and the material to be heated is electrically heated. The product of the frequency of the alternating current supplied to the annular transformer and the number of turns of the annular transformer is set to a constant ratio, for example, 0.8 or more and 1.2 or less with respect to the product of the rated frequency of the annular transformer and the minimum number of turns. Therefore, when the number of turns is changed by switching the tap, the frequency is changed accordingly, whereby the magnetic flux density is maintained at a value within a predetermined range, and magnetic saturation can be prevented.

[0011]

FIG. 2 is a diagram showing an embodiment of the mechanism of the electric heating device according to the present invention. An auxiliary roll R1 lined with a rubber material or the like and a conductive roll electrode R2 are arranged on the entry side of the feed passage L of the material to be heated W with the material to be heated W interposed therebetween. Similarly, on the exit side, an auxiliary roll R3 and a roll electrode R4 are provided to face each other. The material to be heated W is
For example, it is a conductive metal plate such as a steel plate. By using the auxiliary rolls R1 and R3 as described above, the material to be heated W comes into contact with the peripheral surface of a predetermined range of the roll electrodes R2 and R4 and comes into surface contact, so that the allowable current value that does not generate spark is large. A conductive member 14 is connected between the roll electrodes R2 and R4 via sliders S1 and S2.

A choke CH is provided on the entrance side of the feed passage so that voltage does not leak from the heating zone to the entrance side. Further, immediately before the choke CH, the grounding roll R0
1, R02 is provided, and the entrance side is grounded to maintain safety.

Roll electrodes R2, R4 and auxiliary roll R
1, R3 has an axial length greater than the width of the material to be heated W,
The respective peripheral surfaces are disposed so as to face each other with a predetermined gap through which the material to be heated W can pass while contacting the respective peripheral surfaces with the feed passage L interposed therebetween.

The conductive member 14 is formed of a good conductive material such as a copper material having a predetermined width and thickness. Conductive member 14
Are arranged on both sides of the annular transformer close to the annular transformer. The sliders S1 and S2 are connected to both ends of the conductive member 14, respectively, and are slidably contactable with a power receiving unit provided on a rotating shaft of a roll constituting each of the roll electrodes R2 and R4.

Although not shown, a support roll such as a metal roll, a ceramic coating roll, or a ceramic roll may be provided in the feed passage for the material to be heated W.

In this apparatus, an annular transformer 20 is provided as a means for supplying electricity to the material to be heated W. The annular transformer 20 is formed by stacking, for example, a silicon steel sheet having properties suitable as a magnetic path as a square-shaped member 22 as shown in FIG. And the primary coil 24, and the inside of the ring forms a feed passage L for the material to be heated W. That is, the size of the cross-section space in the ring depends on the distance in which the material to be heated W moves in the width direction, that is, the swaying distance, the undulation in the up and down direction, for example, the wave or flutter of a thin steel plate and the catenary. It is set so that it can pass in a non-contact state in consideration of the deflection of the material to be heated W and the like.

The annular transformer 20 may have a configuration as shown in FIG. That is, the space inside the ring of the iron core 22 is made a little larger, and a protective partition wall 26 is provided in the ring so as to surround the feed passage L of the material to be heated W and to have an annular shape concentric with the iron core 22. The protective partition 26 has one layer or two layers as shown. When the protective partition wall 26 has a single layer, a non-magnetic material, for example, a metal material such as stainless steel is used.
The material to be heated W is prevented from being damaged by coming into contact with the primary coil 24 due to shaking when passing through the transformer 20 or splashing at the time of an accident such as breakage. When the protective partition wall 26 has two layers, the non-magnetic metal material is used for the inner layer 26a and the heat insulating material, for example, the heat insulating fiber, is used for the outer layer 26b. The primary coil 24 is prevented from being damaged by heat. If the material to be heated W is unlikely to damage the primary coil 24, a single layer may be formed only of the heat insulating material to prevent the primary coil 24 from burning. Note that the primary coil 24 may be formed of a tube material, and the cooling water for cooling the primary coil 24 may be passed through the pipe.

FIG. 1 is a diagram showing a circuit for supplying a voltage to the annular transformer 20 of the apparatus shown in FIG. The three-phase alternating current supplied from the three-phase alternating current power supply 40 is converted into a single-phase alternating current by the frequency phase number converter 42 and is also converted into a predetermined frequency. The predetermined frequency f obtained by the frequency phase number converter 42
Is sent to the tap changer 50. The tap changer 50 has output terminals connected to a plurality of predetermined positions of the primary winding of the annular transformer 20 as shown in FIG.
In this embodiment, the primary winding has output terminals connected to six positions, and by connecting any of the switches 50a, 50b, and 50c, the number of turns n1 of the primary winding of the annular transformer 20 is changed.

The tap conversion control unit 46 includes the ring transformer 20
Is a control unit for controlling the tap switching for changing the number of turns n of. The tap conversion control unit 46 sets the number of turns n1 of the annular transformer 20 according to the cross-sectional area of the material to be heated W, and outputs a tap switching control signal to the tap switch 50.
The setting of the number of turns n1 by the tap conversion control unit 46 and the switching of taps by the tap changer 50 based on the setting are as follows.
This is performed, for example, when the energization is temporarily stopped at the connection portions of the materials to be heated W having different sizes.

The frequency conversion control unit 44 sets the frequency f according to the number of turns n1 of the annular transformer 20 set by the tap conversion control unit 46, and outputs a frequency setting signal to the frequency phase number converter 42. The frequency f is set such that the set number of turns n1 and the frequency f satisfy the expression 0.8 ≦ f · n1 / fs · ns ≦ 1.2.

That is, the set number of turns n 1 and frequency f
Is in the range of 0.8 to 1.2 with respect to the product fs · ns of the rated frequency fs and the minimum number of turns ns. For example, the frequency f is set so that f · n1 / fs · ns = 1. The number of turns n1 set in this way
The ratio of the product f · n1 of the frequency f to the product fs · ns of the rated frequency fs and the minimum number of turns ns is set to be approximately 1. Therefore, the product f · n1 of the number of turns n1 and the frequency f is set to one.
Is almost constant. Therefore, the magnetic flux density B is given by the formula B
= E1 /4.44f·n1 · S, f · n1 is almost constant, so there is almost no change in the magnetic flux density B due to the change in the number of turns. Therefore, the iron core does not become magnetically saturated due to the change in the number of turns, and it is not necessary to increase the cross-sectional area S of the annular transformer 20 in order to prevent magnetic saturation.

The tap changer 50 is a tap conversion controller 46.
The taps are switched based on the tap switching signal sent from the controller, and a predetermined number of turns n1 is set. On the other hand, the frequency phase number converter 42 sets the frequency f based on the signal sent from the frequency conversion control unit 44 so that, for example, f · n1 / fs · ns = 1.

The single-phase AC having a predetermined frequency f obtained by the frequency-phase number converter 42 is sent to a tap changer 50, and the primary AC of the annular transformer 20 is passed through the tap changed by one of the switches 50a, 50b, 50c. Supplied to the winding.

The overall control section 48 is a control section for controlling each section of the apparatus, and the tap conversion control section 46 according to the heating conditions.
To output a control signal. Further, the voltage and current values supplied to the ring transformer 20 are set and output to the frequency phase number converter 42.

The AC supplied from the three-phase AC power supply 40 is
It is converted into a single-phase alternating current of a predetermined frequency by the frequency phase number converter 42,
0 primary winding 24. When a predetermined voltage is applied to the primary winding 24 of the annular transformer 20, the transformer 2
A secondary voltage is induced in the material to be heated W corresponding to the next side, and the material to be heated W is electrically heated. By switching the taps in this manner, the voltage induced in the material to be heated W can be adjusted. Further, the three-phase AC power supply 40 may be a power supply having a power control switch.

In FIG. 2, when power is supplied to the annular transformer 20, a secondary voltage is induced in the material to be heated W, and the material to be heated W
The secondary current generated on the conductive member 14 flows through the conductive member 14 connected via the sliders S1 and S2 as a return line.
In this case, since the resistance of the conductive member 14 is set to be significantly smaller than the resistance of the material to be heated W, most of the current is consumed for heating the material to be heated W, and the loss in the conductive member 14 is reduced. Few. Therefore, while the material to be heated W is efficiently energized and heated, the voltage generated in the material to be heated W is almost consumed inside the material to be heated W,
The voltage applied to the energizing rolls R2, R4 and the conductive member 14 is extremely low, so that damage to equipment disposed around the heating device can be prevented and worker safety can be maintained.

In this apparatus, the annular transformer 2
Since the conductive members 14 are arranged on the upper and lower sides of the transformer 0, the magnetic coupling between the conductive member 14 and the transformer 20 is good, and the inductance can be reduced. Therefore, since the power factor is good, the efficiency of heating is high.

FIG. 3 is a view showing another embodiment of the mechanism of the electric heating device of the present invention. In this apparatus, a metal bath 30 is provided instead of the roll electrode R4 of the apparatus in FIG. The metal bath 30 is configured by filling a bath tank 31 with a molten metal 32, and an end of the conductive member 14 is immersed in the molten metal 32. The material W to be heated and fed by being heated is changed in direction by the direction change roll R5, and the molten metal 32 is heated.
It is immersed in the inside, the direction is changed by the direction change roll R6, and it is discharged. Further, the conductive member 14 is provided with a roll electrode R
1. Immediately after R2, the upper part 14a is divided into a lower part 14b.
Immediately after the direction change roll R5, the upper part 14c and the lower part 14d are again divided into an upper part 14c and a lower part 14d.
d is respectively immersed in the molten metal 32.

Therefore, the metal bath 30 has the same function as the roll electrode R4 of FIG. 2, and the voltage induced in the material W to be heated by the annular transformer 20 is applied to the conductive member 14 via the roll electrode R2 and the metal bath 30. And the material to be heated W is heated.

Although not mentioned in the description of the above embodiment,
Needless to say, the temperature control for the material to be heated W is performed. That is, the input to the transformer 20 is given in advance so that any one of the required power, the required current, and the required voltage previously determined from the size, the feed rate, the specific heat, the predetermined temperature rise temperature, and the like of the workpiece W is given to the workpiece W. There is a case where a preset method of setting and operating is adopted. Although not shown, the temperature of the material to be heated W is measured on the outlet side of the apparatus, and when there is a difference between the measured value and the expected temperature, the power control switch is operated. Alternatively, a feedback method for adjusting any of power, current, and voltage corresponding to the difference may be adopted.

As an additional remark, the apparatus of the present invention can be arranged not only horizontally or vertically but also at any angle.

[0032]

According to the present invention, the product of the frequency of the alternating current supplied to the annular transformer and the number of turns of the annular transformer is a constant ratio to the product of the rated frequency of the annular transformer and the minimum number of turns. Therefore, when the number of turns of the annular transformer is changed by switching taps, the frequency is changed accordingly, whereby the magnetic flux density is kept within a predetermined range, and the magnetic saturation of the iron core is maintained. Can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram showing one embodiment of an electric heating device of the present invention.

FIG. 3 is a schematic configuration diagram showing another embodiment of the electric heating device of the present invention.

FIG. 4 is a cross-sectional view showing an annular transformer used in the electric heating device.

FIG. 5 is a cross-sectional view showing an annular transformer used in the electric heating device.

[Explanation of symbols]

 Reference Signs List 14 conductive member 20 annular transformer 22 square member 24 primary coil 30 metal bath 40 three-phase AC power supply 42 frequency phase number converter 44 frequency conversion control unit 46 tap conversion control unit 50 tap changer R1, R3 auxiliary roll R2, R4 Roll electrode S1, S2 Slider W Material to be heated L Feed path

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C23C 2/02 C23C 2/02

Claims (6)

(57) [Claims] 1. A continuously fed material to be heated is brought into contact with a roll electrode disposed on an entrance side of a feed passage of the material to be heated, and a conductive mechanism provided on an exit side of the material to be heated is provided. Contacting, an annular transformer is arranged between the roll electrode and the conductive mechanism, and the annular transformer is formed so that the inside of the ring becomes a feed passage of the material to be heated. In an electric heating device that heats the material to be heated by an induced voltage, the device includes: a winding number setting unit that sets a number of windings of the annular transformer; and a frequency setting unit that sets a frequency of an alternating current supplied to the annular transformer. The frequency setting means includes: a product of a frequency of an alternating current supplied to the annular transformer and a number of turns of the annular transformer, wherein a product of a rated frequency of the annular transformer and the annular transformer Wherein the frequency of the alternating current supplied to the annular transformer is set so as to be a fixed ratio with respect to the product of the minimum number of turns of the heating device. 2. The frequency setting means according to claim 1, wherein a product of an AC frequency supplied to said annular transformer and a number of turns of said annular transformer is a product of a product of a rated frequency of said annular transformer and a minimum number of turns of said annular transformer. The current-carrying heating device according to claim 1, wherein the frequency of the alternating current supplied to the annular transformer is set so as to be in a range of 0.8 or more and 1.2 or less. 3. The energization heating device according to claim 1, wherein the number-of-turns setting means changes the number of turns of the annular transformer when the supply of alternating current to the annular transformer is stopped. 4. The electric heating device further includes: a roll electrode disposed on an entrance side of a feed passage of the material to be heated;
2. A conductive member for connecting to a conductive mechanism provided on an outlet side of the material to be heated, wherein the conductive member is arranged close to an outer periphery of the annular transformer. The heating device according to any one of claims 1 to 3. 5. The current-carrying heating device according to claim 1, wherein the conductive mechanism is a roll electrode disposed on an exit side of a feed passage of the material to be heated. 6. The conductive mechanism is a metal bath disposed on an exit side of a feed passage of the material to be heated, wherein the material to be heated is fed through the metal bath, and the conductive member has an end portion formed by the metal bath. 5. The device according to claim 4, wherein the device is immersed in a metal bath.
The resistance heating apparatus.