JP2000271762A - Method for heating control of induction heating device and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the overcurrent of a plurality of parallel induction heating coils by respectively detecting heating currents flowing through the induction heating coils and controlling a heating power source using a high current value selected from the heating currents. SOLUTION: A current command value C1 corresponding to a target heating temperature is outputted from a heating temperature controller to a heating current adjusting device 22. A current signal i1 of the system of a first induction heating coils 11a, 11b is compared with a current signal i2 of the system of a second induction heating coils 12a, 12b by a heating coil current discriminating circuit 21, a higher current signal is selected and is fed back to the heating current adjusting device 22 as a current actual result signal iFB. In the heating current adjusting device 22, a voltage command value C2 wherein the current command value C1 becomes equal to the current actual result signal iFB is outputted to a heating voltage adjusting device 23. A phase control signal C3 wherein the current command value C2 becomes equal to a voltage actual result signal VFB is outputted by the heating voltage adjusting device 23 to control the phase of a heating power source 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating control method for an induction heating device and an apparatus therefor.

[0002]

2. Description of the Related Art A conventional hot rolling process for continuously producing a hot-rolled steel strip is generally constituted as shown in FIG. That is, the slab heated to a uniform temperature in the heating furnace 1 is formed on the slab surface by the descaler 2 after extraction.
Next, the scale (oxide film) is removed, and the sheet is roughly rolled into a sheet bar having a sheet thickness of about 20 to 50 mm by a rough rolling machine 3 including a plurality of stands. The sheet bar is wound and rewound by a single sheet bar coiler 4, and the tail end of the preceding sheet bar and the tip end of the succeeding sheet bar are butt-joined by a joining device 5, and then the induction heating device 6 After the both edge portions are heated to a predetermined temperature, a finishing mill 7 composed of a plurality of stands is finished to a predetermined thickness, cooled by a hot run table 8 and adjusted to a predetermined material. It is wound up.

The induction heating device 6 used here is shown in FIG.
As shown in the figure, the first induction heating coils 11 which are respectively arranged above and below the edge of the sheet bar S and are connected in series
a, 11b, and second induction heating coils 12a, 12b, which are also connected in series, are connected in parallel to the heating power supply 10, and current detectors 13a, 13b detects the load current. One of the current detectors 13a, 13b, for example, the current detector 13a on the first induction heating coil 11a, 11b side.
Heating control device 14 as a representative of the load current signal detected in
And the heating power supply 10 is controlled so as to reach the target heating temperature Ts set by the heating control device 14. Reference numerals 15a and 15b denote oscillation capacitors connected in parallel to the first induction heating coils 11a and 11b and the second induction heating coils 12a and 12b, respectively, 16 a voltage detector, and 17 a voltage indicator. is there.

[0004]

However, in the conventional induction heating apparatus 6, as described above, the first induction heating coil is operated only by the detection signal of one current detector 13a.
11a, 11b and the second induction heating coil 12a, 12b.
When the heating control of two coils is performed at the same time, there are the following problems.

That is, a second induction heating coil of a system to which a current detector 13b not used for control is connected.
The current i ₂ flowing through 12a and 12b is the first induction heating coil.
11a, when greater than the current i ₁ flowing through 11b, even if the current i ₂ is greater than the rated current value, if the state in which the other current i ₁ has not reached the rated current value Then, the heating control is determined to be normal and is continued as it is. Therefore, the second induction heating coil
The burnout prevention circuits of the circuits 12a and 12b are activated to stop the operation, which hinders stable operation of the induction heating device 6.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art described above, and has a heating control method for an induction heating apparatus and an apparatus therefor which can prevent overcurrent of a plurality of parallel induction heating coils. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a heating control method for an induction heating apparatus comprising a plurality of induction heating coils for heating both edges of a sheet bar to a predetermined temperature connected in parallel to a heating power supply. Detecting a heating current flowing through the induction heating coil, selecting a high current value from the heating current, and controlling the heating power supply using the selected current value. It is a heating control method for an induction heating device, which is a feature.

The present invention also relates to a heating control device for an induction heating device, comprising a plurality of induction heating coils for heating both edge portions of a sheet bar to a predetermined temperature connected in parallel to a heating power supply. A heating current detector that detects a heating current flowing through the heater, a heating voltage detector that detects a voltage of the heating power supply, and a heating coil current determination circuit that selects a higher value from current values detected by the heating current detector. And a heating temperature control device for setting a target heating temperature of both edge portions of the sheet bar, and a current command value from the heating temperature control device and a current value selected by the heating coil current determination circuit are made equal. A heating current regulator for outputting a voltage command signal; and a phase control signal such that the voltage command signal from the heating current regulator and the voltage value detected by the heating voltage detector become equal. A heating control device of an induction heating device comprising a heating voltage regulator for controlling the phase of the heating power output to the, in that it consists of.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG.
FIG. 1 is a schematic view schematically showing a main part of an embodiment of the present invention. In the figure, the same members as those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 1, 20 is a heating temperature controller, 21 is a heating coil current discriminating circuit, 22 is a heating current regulator, and 23 is a heating voltage regulator. 24 is a heating coil overcurrent detector.

Therefore, a current command value C ₁ corresponding to the target heating temperature Ts is supplied from the heating temperature controller 22 to the heating current controller 22.
Is output to On the other hand, the heating coil current determination circuit 21
In the first induction heating coil 11a, and the current signal i ₁ detected by the current detector 13a connected to the system of 11b second induction heating coils 12a, a current detector 13b that is connected to the system of 12b The detected current signal i ₂ is compared and determined, and the higher current signal is selected and fed back to the heating current controller 22 as the current actual signal i _FB .

The heating current controller 22 outputs a voltage command value C ₂ to the heating voltage controller 23 so that the current command value C ₁ and the current actual signal i _FB become equal. Further, the heating voltage controller 23 is also provided with a voltage command value C ₂ and a voltage detector.
A phase control signal C ₃ is output to the heating power supply 10 so that the voltage actual signal v _FB fed back from 16 becomes equal to the heating power supply 10 to control the phase of the heating power supply 10.

The heating coil overcurrent detector 24 inputs detection signals from the current detector 13a and the current detector 13b,
If either of them exceeds the rated current, the heating temperature controller 20
And it has a function of outputting a control signal to the phase control signal C ₃ to zero and the operation is stopped and attempt is made to prevent burnout of the induction heating coil. In this case, the power supply line may be cut off.

In this way, the first induction heating coil 11
Since the load currents flowing through the systems a and 11b and the systems of the second induction heating coils 12a and 12b are always compared and determined, and the higher current value is selected to control the phase of the heating power supply 10, It is possible to easily prevent occurrence of overcurrent due to imbalance of the load between the two induction heating coils. Thereby, both edge portions of the sheet bar S can be stably controlled to the target heating temperature.

In the above-described example, the case where the induction heating coil is a parallel circuit of two systems with respect to the heating power supply has been described. However, the present invention is not limited to this. Needless to say, this can be easily applied.

[0015]

As described above, according to the method and apparatus of the present invention, the higher the load current flowing through a plurality of induction heating coils is selected to control the heating power supply to control the load between the induction heating coils. Since the occurrence of overcurrent due to imbalance is prevented, both edge portions of the sheet bar can be stably controlled to the target heating temperature, which greatly contributes to the improvement of the quality of rolled products.

[Brief description of the drawings]

FIG. 1 is a schematic diagram schematically showing a main part of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a conventional example of a continuous hot rolling line.

FIG. 3 is a schematic view showing a conventional example of an induction heating coil.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Descaler 3 Rough rolling mill 4 Sheet bar coiler 5 Joining apparatus 6 Induction heating apparatus 7 Finishing rolling mill 8 Hot run table 9 Coiler 10 Heating power supply 11a, 11b First induction heating coil 12a, 12b Second induction heating coil 13a, 13b Current detector 14 Heating control device 15a, 15b Oscillating capacitor 16 Voltage detector 17 Voltage indicator 20 Heating temperature control device 21 Heating coil current discriminating circuit 22 Heating current regulator 23 Heating voltage regulator 24 Heating coil overcurrent Detector S Sheet bar

Claims (2)

[Claims] 1. A heating control method for an induction heating device, comprising a plurality of induction heating coils for heating both edges of a sheet bar to a predetermined temperature connected in parallel to a heating power supply, wherein a heating current flowing through the induction heating coil is provided. Respectively, a step of selecting a high current value from among the heating currents, and a step of controlling the heating power supply using the selected current value. Control method. 2. A heating control device for an induction heating device, comprising a plurality of induction heating coils for heating both edges of a sheet bar to a predetermined temperature connected in parallel to a heating power supply, wherein a heating current flowing through the induction heating coil is provided. A heating voltage detector for detecting a voltage of the heating power supply, a heating coil current discriminating circuit for selecting a higher value from current values detected by the heating current detector, and a sheet bar. A heating temperature control device for setting a target heating temperature of both edges of the heating temperature control device, and a voltage command signal such that a current command value from the heating temperature control device is equal to a current value selected by the heating coil current determination circuit. A heating current regulator to be output; and a phase control signal output so that a voltage command signal from the heating current regulator and a voltage value detected by the heating voltage detector become equal. Heating control device of an induction heating device comprising a heating voltage regulator for controlling the phase of the heating power, in that it consists of.