JPS628496A - Temperature controller for electric furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an apparatus that can optimally control the temperature of an electric furnace.

[Technical background of the invention and its problems]

Electric furnaces are generally used for small to medium scale steel manufacturing, etc. In this electric furnace, the temperature of the heated material (molten steel temperature) is kept constant so that it does not deviate from the standard temperature in order to stabilize the product and improve quality. It is desirable to maintain the

Conventional temperature control devices for electric furnaces include those in which a program pattern based on the secondary voltage and current setting values of the furnace transformer is stored in advance in a microcomputer, and the power is controlled according to this program pattern. It is known that the temperature is controlled by constantly monitoring the wall temperature and feeding back power operation proportional to the deviation from the reference temperature.

However, in the case of control based only on the former program pattern, if the furnace wall temperature deviates from the reference temperature due to various factors, it becomes difficult to bring the furnace wall temperature closer to the reference temperature.

In addition, in the case of the latter constant temperature control, Fig. 3<A
) and (B), even if the electric power is held constant, stable control cannot be achieved due to the so-called hunting phenomenon in which the temperature of the heated material constantly rises and falls relative to the reference temperature.

As a result, conventional temperature control devices for electric furnaces have the problem of not being able to stabilize products and improve quality. .

[Purpose of the invention]

The present invention was made based on the above circumstances, and its purpose is to perform stable humidity control by performing control based on detected temperature until the reference temperature is reached, and switching to electric power control when the reference temperature is reached. The purpose of the present invention is to provide a temperature control device for electric furnaces that can stabilize products and improve quality.

[Summary of the invention]

In order to achieve the above object, the present invention includes: a temperature detection means for detecting the temperature of a non-heated material in an electric furnace; a power detection means for detecting electric power supplied to the electric furnace; and a detected heated vJ humidity temperature 33tv. = A first control means that controls the supplied power so as to match the temperature, and a second control means that maintains and controls the power when the temperature of the heated material reaches the reference temperature.
a control means, and when the temperature of the heated material reaches the reference temperature and is within a predetermined temperature range with respect to the reference temperature, the second control means is operated;
The gist of the present invention is to include an operation control means for operating the first control means at other times.

[Explanation of Examples]

Hereinafter, a preferred embodiment of the device according to the present invention will be described based on the drawings.

In FIG. 1, a power operating device 1 has a built-in furnace transformer, thyristor (none of which are shown), etc., and is used for tap switching of the furnace transformer to which a high voltage of 10,000 to several tens of thousands of volts is applied. A predetermined power operation is being performed.

The power controller 1 is also provided with a power sensor 3, which sequentially detects the power supplied to the electric furnace.

The high voltage that has undergone power operation is applied to the electrode rods 7a, . . . provided in the electric furnace 7 via the secondary current transformer 5, and the material in the furnace is melted and refined by the arc heat.

A thermocouple 9 is attached to the furnace wall of the electric furnace 7.
As a result, the furnace wall temperature of the electric furnace 7 is constantly detected.

The detected furnace wall temperature is measured by the thermoelectric temperature changer 11.
After being converted into a direct current in units of A, it is taken into the temperature control device 20 as detected temperature T1 data.

The temperature control device @20 includes a temperature monitoring device 21, first and second PID regulators 23, 25, and a changeover switch 27.

The temperature monitoring device 21 has the temperature of the material to be heated which corresponds to M (
A reference temperature) To is stored, and it is monitored whether the detected temperature Ti has reached this reference temperature TO. Further, when the detected temperature Ti reaches the reference temperature TO, it is monitored whether the detected temperature T+ is within a predetermined temperature range α of the reference temperature TO. Based on these monitoring results, a switching command is output to the changeover switch 27. Furthermore, reference temperature TO data is outputted from this temperature monitoring device 21 to the first PtD regulator 23 .

The PID regulators 23 and 25 are constructed of well-known circuits, and the first PID regulator is configured to control the detection temperature T: and the reference temperature TO.
The optimum power operation port can be determined by calculating the deviation from the current value and performing PID calculation on the deviation.

Further, the second PID controller calculates a deviation between the detected power Pi detected by the power sensor 3 and the power Po at the time when the reference temperature Ti is reached (hereinafter referred to as reference power), and performs PID calculation on the deviation. The optimal power operation ω can be obtained by applying .

This embodiment has the above configuration, and its operation will be explained below.

The furnace wall temperature of the electric furnace 7 is sequentially detected by the thermocouple 9 and inputted to the temperature monitoring device 21 and the first PID regulator 23 in the temperature control device 20 via the thermoelectric temperature converter 11.

Then, the first PI-D regulator 23 corrects the power based on the detected temperature Ti until the detected temperature Ti reaches the reference temperature TO (point A in FIG. 2(A)). This allows temperature control to be performed without being affected by voltage fluctuations occurring in the furnace transformer in the power controller 1.

. When the furnace wall temperature Ti reaches the reference humidity TO, a switching command is output from the temperature monitoring device 21 to the changeover switch 27. Then, the contact pieces S1 and S2 of the changeover switch 27 are both switched to the right side in the figure, and the control based on the detected temperature Ti starts to be controlled based on the detected electric power Pi.

Then, in the second PID regulator 25, PID control is performed based on the deviation between the reference power po and the detected power Pi, and the power of the power controller 1 is optimally controlled by the power controller (second (See figure (B)).

This makes it possible to avoid the hunting phenomenon that occurs near the temperature TO.

Meanwhile, the temperature monitoring device @21 monitors the detected temperature Ti, and the detected temperature T1 is the reference temperature T.

When the predetermined temperature +1 width α is exceeded, a switching command is outputted to the changeover switch 27 again, and the intercepts 81 and 82 are switched to the left in the figure. As a result, control based on the detected temperature Tit is performed again until the reference temperature To is reached.

In this way, in this embodiment, the detected temperature Ti is set to the reference temperature TO.
Until the reference temperature To is reached, control is performed based on the detected temperature Ti to avoid the influence of the voltage fluctuation of the furnace transformer, and when the reference temperature To is reached, the furnace wall is controlled based on the detected power Pi. Since the influence of the temperature hunting phenomenon can be avoided, stable temperature control is possible. It becomes possible to unite them, stabilize the product, and improve the quality of the product.

Although this embodiment shows a hardware configuration centered on a PID controller, the present invention is not limited to this.
Software control may be performed by a microcomputer in which a control program is stored in advance.

Further, the electric furnace is not limited to an arc furnace, and may be an induction type electric furnace that melts and refines the material to be heated using a heater.

〔Effect of the invention〕

As explained above, according to the present invention, the control is performed based on the detected temperature until the detected temperature reaches the reference temperature, and when the detected temperature reaches the reference temperature, the control is performed based on the detected power, so it is always stable. As a result, it becomes possible to stabilize the product and improve the quality of the product.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of an embodiment of the device according to the present invention, Fig. 2 (A) and (B) show the power characteristic curve and temperature characteristic curve of the device of the present invention, and Fig. 3 (Δ) and (B
) are the power characteristic curve and temperature characteristic curve of the conventional device. 1... Power operation device 3... Power sensor 7... Electric furnace 9... Thermal lightning pair (temperature sensor) 20... Temperature control device 21... Temperature monitoring device 23... First PID regulator 25...Second PID regulator 27...Switching switch

Claims (4)

[Claims] (1) Temperature detection means for detecting the temperature of the material to be heated in the electric furnace; power detection means for detecting the electric power supplied to the electric furnace; a first control means for controlling the temperature of the heated material, a second control means for holding and controlling the electric power when the temperature of the heated material reaches the reference temperature; activating the second control means when the temperature is within the temperature range;
A temperature control device for an electric furnace, comprising: operation control means for operating the first control means at other times. (2) The temperature control device for an electric furnace according to claim 1, wherein the temperature of the heated material is a furnace wall temperature of the electric furnace. (3) The temperature control device for an electric furnace according to claim 1, wherein the first control means is constituted by a PID controller. (4) The temperature control device for an electric furnace according to claim 1, wherein the second control means is constituted by a PID controller.