JPH0763029B2 - Actual input power control method for local heating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a heating device used for local heating, and a method for controlling actual input power for effective heating.

B. SUMMARY OF THE INVENTION The present invention relates to a method for controlling actual heating power for local heating, in which a power source is set so that the effective heating power derived from the output power from the power source, the electric circuit loss, and the loss in the load matches the set heating power. By controlling the heating power, highly accurate heating power control is performed.

C. Conventional technical problems In the local heating, an electron tube type oscillating device will be described as an example. With electron tube oscillators, there is no means for easily measuring the high frequency power value at the production site because the frequency is high in the case of 20 kHz or higher.

Therefore, since the high frequency output power of the electron tube (hereinafter referred to as the oscillation tube) cannot be measured directly, instead of this, the DC input value is measured at the input side of the oscillation tube, and this value indirectly controls the high frequency output side. Is performed, and the required equipment rating is estimated and the power is controlled in the line instead of the high frequency output value. Therefore, since the control is indirect, there is a drawback that the accuracy is low.

Further, when using a DC input value for automation, for example, in the same welding line (apparatus) or heat treatment line, for example, the oscillation efficiency of the oscillation tube (ratio between DC input value and high frequency output value) or transmission Since it is possible to consider the loss fixed, it is possible to manage statistically the actual value even if the load object changes, but if the line and equipment are different, the above-mentioned oscillation The efficiency and transmission loss are also different, and the relationship between the DC input value and the high-frequency output value of another line cannot be applied, so the actual value must be accumulated again for each line.

In any case, the high-frequency power cannot be directly measured and the control is performed by using the indirect DC input or by stacking the actual values, and the input and intermediate loss shown in Fig. 8 cannot be obtained accurately. The actual heating input to the load was only obtained by estimation, and the power could not be controlled with high precision.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a local heating actual input power control method for controlling an actual heating input with high accuracy.

D. Means for Solving Problems The present invention that achieves the above-mentioned object is to obtain the electric circuit loss W _E by calculating the output power from the power source in the no-load measurement in which there is no heating material in the heating element. In addition, there is no effective heating part, or the dummy load with minimal heat generation is measured to calculate the loss W _L in the load by calculating the output power from the power source, and the actual load with heating material present on the heating element is measured. At, the effective heating power is obtained by subtracting the above-mentioned losses W _E and W _L from the output power from the power supply, and comparing this effective heating power with the set heating power, the output power of the power supply is controlled so as to match them. It is characterized by

Recently, instruments capable of high-speed digital storage capable of storing high-speed instantaneous waveforms corresponding to high frequencies have appeared, so that effective value calculation at high frequencies can be performed.

E. Practical Example An example of the present invention will now be described with reference to FIGS. FIG. 1 is an electron tube oscillator circuit diagram for measurement in the method of the present invention. First of all, from this circuit, 1 is a power controller for voltage adjustment, 2 is a transformer, 3 is an inverse converter, 4 is an oscillation electron tube (oscillation tube), and 5 is a reactor.
A low frequency filter composed of 5a and a capacitor 5b for smoothing rectification ripple, 6a a high frequency current choke coil, 6b a DC cut capacitor, 7 and 8 capacitors for forming a tank circuit, 9 a tank circuit for output A matching transformer serving as a transformer, 10 are two grid feedback capacitors, and 11 is a set of a grid choke coil, a resistor, and a capacitor.

In such an oscillation circuit, a resistance voltage divider 12 is connected between the plate of the oscillation tube 4 and the cathode, and the resistance voltage divider 12 can detect an instantaneous plate voltage waveform e _HF .

A high-frequency current transformer 13 is provided on the plate side of the oscillator 4, and the current transformer 13 causes an instantaneous plate output current waveform.
i _HF can be detected.

Further, the tank circuit formed by the capacitors 7 and 8 and the matching transformer 9 is provided with a large current high frequency current transformer 14, and the resonance circuit current waveform i _t can be detected.

Resistance voltage divider 12, high frequency current transformer 13, high current high frequency current transformer 14
Voltage waveforms and current waveforms e _HF from, i _HF, i _t is the data storage of the measurement of a few Hz since a high frequency is performed, the waveform data is stored in the digital memory 16 via multiplexer 15. Thereafter processing section 17 transfers and calculation of the waveform data is performed in the effective value of such high-frequency power P _HF and current I _t is obtained.

In FIG. 1, the secondary side of the matching transformer 9 is connected to the heating coil H. In contrast to this coil H, P is an object to be heated, which is a pipe in the embodiment shown in FIG.

The measuring method will be described with reference to the circuit diagram of FIG. Driving the oscillator, the voltage e _HF and high frequency current by the resistance voltage divider 12
i _HF is detected, waveform data is stored in the digital memory 16, and each effective value is calculated by calculation. as well as Ask for. Here, T is the period, and the power P _HF changes depending on the state of the load impedance.

On the other hand, the high-frequency power P _HF1 obtained with no load is the loss of the transmission circuit (electrical circuit) that consists of transmission loss and coil loss.
It is equal to W _E and is proportional to the effective power I _t calculated by the high-current high-frequency current transformer 14 from the high-frequency current waveform i _t to the A-th power. Here, A is a numerical value such as 1.8 to 2.2. Thus, if the proportional constant is K _E , P _HF1 = W _E = K _E ▲
I ^A _t ▼ formula is satisfied of. Here, P _HF1 is obtained by actual measurement and calculation of E _HF and I _HF, and I _t is also obtained by actual measurement and calculation.

Next, in an induction type device having a heating coil H as shown in FIG. 2 (b), a dummy load which is an object to be heated P cut so as not to form a heating part, that is, not to form an energizing circuit. (Pipe) _{Find the} high frequency power P _HF2 from I _HF / E _HF at P _a . In this case, the power _obtained by subtracting the above-mentioned transmission circuit loss W _E from the high-frequency power P _HF2 becomes the loss component W _L in the load of the sum of the outer peripheral pipe loss and the inner peripheral pipe loss,
Moreover it becomes a value A th power minus the P _HF2 of the effective value I _t obtained by the calculation by the high frequency current i _t by a large current high frequency current transformer 14 is obtained in the form of _{W L = K L · ▲ I} B t ▼ . That is, when determining the loss W _L of the pipe _{P a, W L = P HF2} -W E = P HF2 -
^{_{K L · ▲ I A t ▼}} = a ^{_{K L · I ▲ B c ▼}} .

Then the pipe P _a which is an object to be heated as of FIG. 2 (a) is inserted into the heating coil H and performs measurement of the time of actual load, V
The character-shaped edge portion is heated and melt-bonded. In this case, the high frequency power P _HF3 of the oscillator tube 14 at the actual load is the effective heating power.
Let P _w be the following equation.

_{P HF3 = P w + W E} + W L P w + K E ▲ I A t ▼ + K L ▲ I B t ▼ As a result, P _HF3 is Motomari with the actual load at the time of the _{I HF · E HF, W E} ,
Since W _{L is} also obtained, the effective heating power P _w can be obtained.

After measuring the effective heating power, the comparator 18 compares the effective heating power P _w with the set heating power P _H as shown in FIG. 3, and the effective heating power P _w is the set heating power P _w. It is calculated by the control unit 19 so that it becomes _H , and the power source (in this embodiment, the power controller 1 and the oscillation tube 4 shown in FIG. 1)
To obtain the output power P _H. Originally, the effective heating power P _w should be able to directly represent the theoretical amount of heat generated in the heated area, but in reality it is a value proportional to the net heating power of this amount of heat generated, so a comparison operation is performed using this value to calculate the power supply. It is in control. FIG. 3 is a diagram in which the comparator 8 and the control box 19 are attached to the circuit of FIG. 1, and is simplified from FIG. 1 in order to display the arithmetic function.

Although the description of FIGS. 1 to 3 is based on the induction type oscillation tube, the present invention is also applicable to contact type electrification heating in which a contact is applied to a heating portion, and the oscillation tube is also used. The present invention can be applied not only to those having a power supply section, but also to the heating of medium frequency inverters, thyristor switches, and commercial frequencies described later. As a result, the power measuring means can be a simple block as shown in FIG. 4, and the effective heating power can be obtained by the loss measurement by PT and CT for the output power P _HF from the power source.

In the above-described embodiment, the electric power is measured by the dummy load by using the pipe P _a shown in FIG.
The P _HF2 and the loss W _L were obtained. The object to be heated forms a conducting circuit as shown in Fig. 5 (a), or forms a conducting circuit in the plate-like one shown in Fig. 6 (a). in case of,
In order to reduce the heat generation as much as possible to reduce the heating power, the copper pipe Cu is inserted to pass water (Fig. 5 (b)) in the example of Fig. 5, and the plate of the plate is used in the example of Fig. 6. The copper pipe Cu is closely attached to both sides and water is allowed to pass therethrough (Fig. 6 (b)) to suppress the effective heating power and obtain the load loss.

Further, FIG. 7 shows three examples of the power supply unit, and heating power control can be performed even in a local heating device using these power supply units. Here, FIG. 7 (a) is a commercial frequency heating power source,
(B) shows a thyristor switch heating power supply, and (c) shows a medium frequency inverter heating power supply.

F. Effects of the Invention As described above, according to the present invention, the actual input active power control can be precisely performed, the change due to the disturbance can be coped with, and the control can be performed under the unsteady use condition without waste. Optimal and accurate heating can be performed, and the product quality can be maintained.

[Brief description of drawings]

1 to 7 show an embodiment of the present invention. FIG. 1 is a circuit diagram for measurement, FIG. 2 (a) is an actual load heating state diagram, and FIG. 2 (b) is a dummy load heating state. Fig. 3, Fig. 3 and Fig. 4 are control block diagrams, Fig. 5 (a) (b) and Fig. 6 (a).
(B) is a heating state diagram of an actual load and a dummy load, FIGS. 7 (a), (b), and (c) are circuit diagrams of a power supply unit, and FIG. 8 is a block diagram showing a loss of local heating. In the figure, 18 is a comparator and 19 is a control unit.

Claims (1)

[Claims] 1. An electric circuit loss W _E is obtained by calculating the output power from a power source in a no-load measurement in which there is no heating material in the heating element, and there is no effective heating part in the heating element, or heat generation is suppressed as much as possible. The loss W _L in the load is calculated by calculating the output power from the power source by measuring the dummy load, and further the loss W _E , W _L from the output power from the power source by measuring the actual load when the heating material is present in the heating _element. The effective heating power for local heating is controlled by calculating the effective heating power by subtracting, and comparing the effective heating power with the set heating power and controlling the output power of the power supply so as to match them.