JPH0541268A - Electric current heating device - Google Patents

Abstract

PURPOSE:To prevent an abnormal rise or drop of the plate temperature owing to an unfavorable current flowing to a material to heat near a connecting part, in a device to heat a material to heat by an electric current heating by using a circular transformer. CONSTITUTION:When a material to heat is changed, the winding number n of a circular transformer 20 which is converted through a tap converter 50 by a tap converter controller 46 is set, and the frequency f fed to the transformer 20 is set by a frequency converter controller 44 according to the winding number n. And for the period that the next material to heat reaches to the position to control to heat after the winding number is converted, the voltage or the current fed to the circular transformer 20 is controlled to let the same current flow to the material to heat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating device for electrically heating a mass-produced electrically conductive material to be continuously fed at a high speed, for example, as a preheat treatment for galvanizing a steel material. The present invention relates to an electric heating device for heating.

[0002]

2. Description of the Related Art A material to be heated having electrical conductivity, for example, a steel material, is continuously fed at high speed for various purposes such as preheating for plating, annealing, and hardening, and an alternating current is applied to the material to be heated. An apparatus for heating a material to be heated by resistance heating is known.

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

In such an electric heating device, for example, the primary winding is wound multiple times over the entire length of the iron core of the 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 heating is controlled according to the material, width, and plate thickness of the material to be heated by supplying power to the primary winding via the selected tap.

[0005]

By the way, the magnetic flux density B which is an important factor in determining the specifications of the annular transformer.
Is the primary AC voltage supplied to the annular transformer E1,
Assuming that the frequency is f, the cross-sectional area of the iron core is S, and the number of turns is n, B = E1 /4.44f·n·S. It is an essential condition in designing the annular transformer that the magnetic flux density B is not saturated.

Therefore, when the number of turns n is changed, for example, even when the number of turns n becomes small, the magnetic flux density B
In order to prevent saturation of the iron core cross-sectional area S
Must be increased according to the change in. But,
When the cross-sectional area S of the iron core is increased as described above, a large installation space for the annular transformer is required, the installation cost increases, and in some cases, the annular transformer cannot be installed. It is possible to change f.

When the number of turns of the annular transformer is changed according to the material to be heated in this way, the number of turns is changed at a portion where the material to be heated changes when a plurality of types of materials to be heated are fed. Along with this, the voltage and current supplied to the annular transformer are also changed. By the way, when the number of turns of the annular transformer is changed in this way, if a voltage and a current are immediately supplied according to the next material to be heated, an undesired current is mainly supplied to the previous material to be heated. The flow plate temperature rises abnormally,
There was a problem of lowering.

The present invention solves the above problems,
It is an object of the present invention to provide an electric heating device in which, when the number of turns of an annular transformer is changed, the same current as before flows until the next heated material reaches a position where heating is controlled.

[0009]

According to the present invention, there is provided an electric heating apparatus in which a material to be continuously fed is brought into contact with a roll electrode arranged on the inlet side of a feed passage of the material to be heated,
By heating the material to be heated by contacting it with a roll electrode or metal bath provided on the output side, an annular transformer is placed between the roll electrode on the input side and the roll electrode or metal bath on the output side. The inside of the annular transformer serves as a passage for the material to be heated.

The energization heating device includes a voltage / current control means for controlling the AC voltage and current supplied to the annular transformer, and a winding number setting means for setting the winding number of the annular transformer according to the material and size of the material to be heated. Frequency setting means for setting the frequency of the alternating current supplied to the annular transformer according to the number of turns of the annular transformer. The voltage / current control means is
After the number of turns of the annular transformer is changed by the number-of-turns setting means, the voltage or current is controlled so that the same current as that before the change of the number of turns flows through the heated material until the heating control of the next heated material is started. To do.

[0011]

According to the present invention, after the number of turns of the annular transformer is changed, until the heating control of the next material to be heated is started, the same current as that before the number of turns of current is supplied to the material to be heated. The voltage or current is controlled. Therefore, until the next heated material reaches the position where the heating is controlled by the annular transformer, the same current as before flows, so prevent an undesired value of current from flowing through the heated material near the joint. You can

[0012]

FIG. 2 is a view showing an embodiment of the mechanism of the electric heating apparatus of 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 inlet side of the feed path L for the heated material W so as to face each other across the heated material W. Similarly, an auxiliary roll R3 and a roll electrode R4 are provided on the exit side so as to face each other. The material to be heated W is
For example, it is a metal plate having conductivity such as a steel plate. By using the auxiliary rolls R1 and R3 as described above, the material W to be heated comes into contact with the peripheral surfaces of the roll electrodes R2 and R4 in a predetermined range to form surface contact, so that the allowable current value that does not generate spark is large. The conductive member 14 is connected between the roll electrodes R2 and R4 via the sliders S1 and S2.

A choke CH is provided on the inlet side of the feed passage to prevent voltage leakage from the heating zone to the inlet side. Further, immediately before the choke CH, the ground roll R0
1, R02 are provided, and the entrance side is grounded to keep safety.

Roll electrodes R2, R4 and auxiliary roll R
1, R3 have an axial length that is equal to or greater than the width of the material W to be heated,
The respective peripheral surfaces are arranged so as to face each other with a predetermined gap through which the heated material W can pass while being in contact with the respective peripheral surfaces across the feed passage L.

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 in proximity to the annular transformer. The sliders S1 and S2 are connected to both ends of the conductive member 14, respectively, and can be slidably contacted with a power receiving portion provided on a rotation shaft of a roll forming each of the roll electrode R2 and the roll electrode 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 of the heated material W.

In this apparatus, an annular transformer 20 is provided as a means for energizing the material W to be heated. The annular transformer 20 is formed, for example, by forming a silicon steel plate having a property suitable as a magnetic path as a square-shaped member 22 as shown in FIG. 4 and stacking it, and winding it around an iron core having a predetermined length and the inner and outer circumferences of the annulus. And the primary coil 24, and the inside of the ring forms a feed passage L for the heated material W. That is, the size of the cross-sectional space in the annulus depends on the distance in which the material W to be moved moves in the width direction, that is, the wobbling in the width direction, the undulation in the vertical direction, for example, the wave and flap of the plate generated in the case of a thin steel plate, and catenary In consideration of the deflection of the material to be heated W and the like, the material W is set to pass through in a non-contact state.

The annular transformer 20 may have the structure shown in FIG. That is, the inner space of the iron core 22 is made slightly larger, and a protective partition wall 26 is provided in the ring so as to surround the feed passage L for the material W to be heated and to have an annular shape concentric with the iron core 22. The protective partition 26 has one layer or two layers as shown. The protective partition 26 in the case of one layer is made of a non-magnetic material, for example, a metal material such as stainless steel,
This prevents the material W to be heated from coming into contact with the primary coil 24 and being damaged by swaying when passing through the transformer 20 or splashing in an accident such as breakage. In the case of a two-layer protective barrier 26, the non-magnetic metal material is used as the inner layer 26a and the heat insulating material, such as heat insulating fiber, is used as the outer layer 26b. The primary coil 24 is prevented from burning due to heat. Further, when there is no risk of the heated material W damaging the primary coil 24, one layer may be formed of only a heat insulating material to prevent the primary coil 24 from burning. Note that the primary coil 24 may be a pipe material, and cooling water for cooling the primary coil 24 may pass 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 also converted into a predetermined frequency. Predetermined frequency f obtained by the frequency phase converter 42
The single-phase alternating current 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.
The present embodiment has output terminals connected to six positions of the primary winding, and changes the number of turns n of the primary winding of the annular transformer 20 by connecting any of the switches 50a, 50b, 50c.

The tap conversion control unit 46 is a ring transformer 20.
Is a control unit that controls tap switching for changing the number of turns n. The tap conversion control unit 46 sets the winding number n of the annular transformer 20 according to the cross-sectional area of the material W to be heated, and outputs a tap switching control signal to the tap switching unit 50. The setting of the number of turns n by the tap conversion control unit 46 and the switching of the taps by the tap changer 50 based on the setting are performed, for example, when the energization is temporarily stopped at the connecting portion of the heated materials W having different sizes. Done.

The frequency conversion control unit 44 sets the frequency f according to the number of turns n 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 so that the set number of turns n and the frequency f satisfy the expression 0.8 ≦ f · n / fs · ns ≦ 1.2.

That is, the product f · n of the set number of turns n and the frequency f is the product f of the rated frequency fs and the minimum number of turns ns.
The range is 0.8 to 1.2 with respect to s · ns. For example, the frequency f is set so that f · n / fs · ns = 1. Since the ratio of the product f · n of the number of turns n and the frequency f set in this way to the product fs · ns of the rated frequency fs and the minimum number of turns ns is set to be approximately 1, the number of turns n and the frequency are set. The product f · n with f has a substantially constant value. Therefore, in the equation B = E1 /4.44f.n.S, the magnetic flux density B is almost constant, so that there is almost no change in the magnetic flux density B due to the change in the number of turns n. Therefore,
The iron core is not magnetically saturated by the change in the number of turns n,
The cross-sectional area S of the annular transformer 20 for preventing magnetic saturation
Does not have to be large.

The tap changer 50 is a tap conversion controller 46.
The taps are switched based on the tap switching signal sent from, and a predetermined number of turns n 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 · n / fs · ns = 1.

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

The voltage / current controller 52 controls the voltage and current supplied from the frequency / phase number converter 42. This control is particularly performed at the joint between the materials W to be heated, as described later. The overall control unit 48 is a control unit that controls each unit of the present device, and outputs a control signal for changing the number of turns n according to the heating condition to the tap conversion control unit 46. Further, the voltage / current control unit 52 outputs a control signal for setting the values of the voltage and current supplied to the annular transformer 20.

The alternating current supplied from the three-phase alternating current power supply 40 is
It is converted into a single-phase alternating current of a predetermined frequency by the frequency / phase number converter 42, and the ring transformer 2 is passed through the tap changer 50.
0 to the 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 heated material W corresponding to the secondary side, and the heated material W is electrically heated.

When the material W to be heated is changed to a different type, a control signal is output from the overall control unit 48 to the tap conversion control unit 46, and the next heating target is replaced with the number of turns na set up to that point. The number of turns nb for heating the material W is set. In response to this, the tap changer 50 changes the new winding number n.
Set b.

At this time, until the next heated material W reaches the heating control position, that is, until the joint portion between the previous heated material W and the next heated material W reaches the predetermined position. The voltage / current control unit 52 controls the current Ib supplied from the frequency phase number converter 42 so that a current having the same value as the current Ia flowing in the first heating of the heated material W flows in the heated material W. , Ib = Ia.multidot.na / nb or the voltage Vb supplied from the frequency phase converter 42 is changed to Vb = V.
It is controlled to be a.nb / na.

By controlling the current Ib or voltage Vb supplied from the frequency phase converter 42 in this way,
For example, if the supplied voltage Vb is multiplied by nb / na with respect to the original voltage Va, the number of turns n is changed from na to nb, and the heated material W corresponding to the secondary side of the annular transformer 20 has na / n. Since the voltage is changed so that nb times the voltage is generated, nb / na × na / nb = 1, the change in voltage and the change in the number of turns are canceled, and the same voltage as that applied before the change in the number of turns is obtained. The voltage is also applied to the joint portion of the material W to be heated. Therefore, before the next heated material W reaches the position where the heating is controlled, that is, until the joint portion of the heated material W reaches the predetermined position, the current flowing through this portion is changed by changing the number of turns. Can be prevented.

As described above, according to this apparatus, the voltage induced in the material W to be heated can be adjusted by switching the taps, so that the current flowing through the material W to be heated according to the change of the material W to be heated. Can be set and before the next heated material W reaches a position where heating is controlled, that is, until the joint portion of the heated material W reaches a predetermined position,
The current Ib supplied from the frequency / phase number converter 42 is Ib =
Ia.na/nb or voltage Vb is Vb = Va.nb
Since the current is controlled to be / na, the current flowing through the joint portion of the material W to be heated can be made equal to the current up to that point.

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 heated material W, and the heated material W
The secondary current thus generated flows through the conductive member 14 connected via the sliders S1 and S2 as a return line.
In this case, the resistance of the conductive member 14 is set to be significantly smaller than the resistance of the heated material W, so most of the current is consumed for heating the heated material W, and the loss in the conductive member 14 is reduced. Few. Therefore, the material W to be heated is efficiently heated by electricity, and most of the voltage generated in the material W to be heated is consumed inside the material W to be heated,
The voltage applied to the energizing rolls R2, R4 and the conductive member 14 is very low, which can prevent damage to the equipment arranged around the heating device and keep the worker safe.

Further, in this device, the annular transformer 2
Since the conductive members 14 are arranged on both upper and lower sides of 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 heating efficiency is high.

FIG. 3 is a view showing another embodiment of the mechanism of the electric heating apparatus of the present invention. In this apparatus, a metal bath 30 is provided instead of the roll electrode R4 of the apparatus shown in FIG. The metal bath 30 is configured by filling a bath tank 31 with the molten metal 32, and the end of the conductive member 14 is immersed in the molten metal 32. The material W to be heated, which is heated by electrical conduction, is changed in direction by the direction change roll R5, and the molten metal 32
It is dipped in the inside, and the direction is changed by the direction changing roll R6, and then discharged. In addition, the conductive member 14 is a roll electrode R.
1, immediately after R2, is divided into an upper part 14a and a lower part 14b, and is combined into one just before the direction change roll R5,
Immediately after the direction change roll R5, the upper part 14c and the lower part 14d are divided into the upper part 14c and the lower part 14c.
Each d is immersed in the molten metal 32.

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

Although not mentioned in the above description of the embodiment,
It goes without saying that the temperature of the material W to be heated is controlled. That is, an input to the transformer 20 is predetermined so that any one of a required power, a required current, and a required voltage obtained in advance from the size of the heated material W, the feed rate, the specific heat, the predetermined temperature rise, and the like is given to the heated material W. A preset method of setting and operating may be adopted. Although not shown, the temperature of the heated material W is measured on the outlet side of the device, and if there is a difference between the measured value and the planned temperature, the power control switch is operated. Alternatively, a feedback method of adjusting any of power, current, and voltage corresponding to the difference may be adopted.

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

[0038]

According to the present invention, after the number of turns of the annular transformer is changed, the same current as that before the number of turns is passed through the heated material until the heating control of the next heated material is started. To control the voltage or current. Therefore, the same current as before flows until the next heated material reaches the position where the heating is controlled by the annular transformer, so that an undesired value of current is prevented from flowing at the joint between different heated materials. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit of an electric heating apparatus of the present invention.

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

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

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

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

[Explanation of symbols]

 14 conductive member 20 annular transformer 22 square-shaped member 24 primary coil 30 metal bath 40 three-phase AC power source 42 frequency phase number converter 44 frequency conversion control unit 46 tap conversion control unit 50 tap changer 52 voltage / current control unit R1, R3 Auxiliary roll R2, R4 Roll electrode S1, S2 Sliding element W Heated material L Feed path

Claims (7)

[Claims] 1. A continuously fed material to be heated is brought into contact with a roll electrode arranged on the inlet side of a feed passage of the material to be heated, and a conductive mechanism is provided on the outlet side of the material to be heated. A ring-shaped transformer is disposed between the roll electrode and the conductive mechanism, and the ring-shaped transformer is formed so that the inside of the ring serves as a feed passage for the material to be heated. In an electric heating apparatus for heating the material to be heated by an induced voltage, the apparatus comprises voltage / current control means for controlling an AC voltage and current supplied to the annular transformer, and a material and a size of the material to be heated. And a frequency setting means for setting the frequency of the alternating current supplied to the annular transformer in accordance with the number of windings of the annular transformer. Having the voltage / current control means, after the number of turns of the annular transformer is changed by the number of turns setting means, until the heating control of the next material to be heated is started, before the number of turns of the material to be heated is changed. An electric heating device characterized in that the voltage or the current is controlled so that the same current as the above-mentioned current flows. 2. The voltage / current control means sets the number of turns na before being changed by the number of turns setting means, the number of turns nb after being changed, and the voltage supplied to the annular transformer before the number of turns is changed. Vb = Va.n until the heating control of the next material to be heated is started, where Va and current are Ia.
Voltage Vb satisfying b / na or Ib = Ia * na / nb
The electric heating device according to claim 1, wherein a current Ib that satisfies the above condition is controlled so as to be supplied to the annular transformer. 3. The frequency setting means, wherein the product of the frequency of the alternating current supplied to the annular transformer and the number of turns of the annular transformer is the product of the rated frequency of the annular transformer and the minimum number of turns of the annular transformer. The electric heating device according to claim 1 or 2, wherein the frequency of the alternating current supplied to the annular transformer is set so as to fall within a range of 0.8 or more and 1.2 or less. 4. The winding number setting means changes the winding number of the annular transformer when the supply of alternating current to the annular transformer is stopped.
The electric heating device according to. 5. The electric heating device further includes the roll electrode disposed on an inlet side of a feed passage for the material to be heated,
2. A conductive member is provided to connect a conductive mechanism provided on the outlet side of the material to be heated, the conductive member being arranged close to the outer periphery of the annular transformer. The electric heating device according to any one of 1 to 4. 6. The electric heating device according to claim 1, wherein the conductive mechanism is a roll electrode arranged on an outlet side of a feed passage of the material to be heated. 7. The conductive mechanism is a metal bath arranged on an outlet side of a feed passage of the heated material, the heated material is fed through the metal bath, and the conductive member has an end portion. 6. Immersed in a metal bath, characterized in that
The electric heating device according to any one of 1 to 5 above.