JPH01120788A - High frequency heating power control method - Google Patents

Abstract

PURPOSE:To make it possible to close DC input in accordance with effective heat output equired for heating by measuring DC input, operation loss of an oscillation element, loss of an electric circuit, and heat loss of a substance to be heated. CONSTITUTION:DC input P1 to an oscillation circuit is sought by operation from DC voltage obtained from a potential divider 29 and DC current obtained from a shunt 30, and operation loss WOSC of an oscillation element is sought by operation from voltage between elements obtained from a potential divider 31 and current flowing to the element obtained from a current transformer 32. Electric circuit loss WE is sought by operation from a formula which multiplies about square by coefficient of proportion using condensor voltage obtained from the potential divider 33 and a tank circuit current obtained from the current transformer 34, and heat loss WH is sought by operation from a formula which multiplies about square of the condensor voltage or the tank circuit current by coefficient of proportion. And for the required effective heat output PN the DC input Pi is so controlled that it may Pn=Pi (WOSC+WE+WH). Hereby, each loss becomes clear and accurate DC input in accordance with the required effective output is made.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of Application The present invention relates to a high frequency heating device used for local heating.
The present invention relates to a control method in which DC input is applied in accordance with the effective thermal output necessary for heating by measuring the DC input, the operating loss of the oscillation element, the loss of the electric circuit, and the heat loss of the object to be heated.

B. Summary of the Invention The high-frequency heating power control method according to the present invention converts the DC input Pi to the oscillation circuit into a DC voltage obtained from a voltage divider connected between the high voltage line and the common line and a shunt inserted into the common line. The operating loss W of the oscillation element is determined by calculation from the DC current. Calculate So from the inter-element voltage obtained from the voltage divider and the current flowing through the element obtained from the current transformer installed between the oscillation element and the common line, and calculate the electric circuit loss W6 by calculating the high voltage of the tank circuit capacitor. Using the capacitor voltage obtained from the voltage divider connected between the side terminal and the common line, or the tank current gL4 obtained from the current transformer attached to the common line part of the tank circuit, calculate the capacitor voltage or tank circuit current. Calculate the heat loss WH from a formula that multiplies approximately the square of the proportional coefficient, and use the capacitor voltage obtained from the voltage divider or the tank circuit current obtained from the current transformer to calculate the abbreviation of the capacitor voltage or tank circuit current. It is calculated by multiplying the square by the proportional coefficient, and for the required effective heat output PN, 'N = Pl - (wo
By controlling the DC input P so that sc"%"J, it is possible to precisely control the effective heat output 9, and when measuring voltage and current, it is possible to prevent damage to the detection circuit due to high voltage, Furthermore, it is possible to prevent unexpected personal accidents.

C9 Prior Art In high-frequency heating, DC power is supplied from a DC power supply to an oscillation circuit, and the high-frequency power is applied to an object to be heated via a heating element such as a work coil or a contactor. As the oscillation element, an electron tube or a semiconductor element is used.

Conventionally, in this type of oscillation circuit, if the frequency is 20 KHz or more, the frequency is high and the power is large, so there is no means to easily measure the high frequency power value during the heating operation at the production site.

Therefore, the relationship between the DC input value to the oscillation circuit and the high frequency power value applied to the heated object is determined by statistical processing from the actual high frequency heating values, and the DC input value is measured and controlled based on this relationship. was.

D Problems to be solved by the invention However, in the past, the relationship between the DC input value and the high-frequency power value was obtained through statistical processing, which made it difficult to accurately apply the effective thermal output necessary for welding, heat treatment, etc. to the heated object. I can't.

In particular, when automating, (a) For example, within the same welding line (equipment) or the same heat treatment line (equipment), the oscillation efficiency of the oscillation element and the electric circuit loss are fixed, so the number of objects to be heated may be slightly smaller. Even if the actual values change, it can be dealt with by statistical processing of the actual values, but (b) If the line or equipment is different, or if the heated object changes significantly, the oscillation efficiency, electrical circuit loss, and even the heated Since the heat loss of objects is different, the relationship between the past DC input value and high frequency power value cannot be applied, and the actual value is
The troublesome work of layering one layer is required.

In view of the drawbacks of the prior art described above, the present invention provides a direct current input,
The purpose of the present invention is to provide a control method that can input DC input according to the required effective heat output by measuring the operating loss of the oscillation element, the loss of the electric circuit, and the heat loss of the heated object, and further, The purpose of measuring each of the above items is to ensure that the detection circuit is not destroyed by high voltage and that unforeseen personal accidents occur.

Means for Solving Points E and W2B The high frequency heating power control method according to the present invention connects the DC input Pi to the oscillation circuit to the DC voltage obtained from a voltage divider connected between the high voltage line and the common line and the common line. The operating loss W of the oscillation element is determined by calculation from the DC current obtained from the inserted shunt. So is calculated from the inter-element voltage obtained from the voltage divider and the current flowing through the element obtained from the current transformer installed between the oscillation element and the common wire, and the electric circuit loss toughness is determined by calculating the high voltage of the capacitor in the tank circuit. Using the capacitor voltage obtained from the voltage divider connected between the side terminal and the common line, or the tank circuit current obtained from the current transformer attached to the common line part of the tank circuit, approximately 2 of the capacitor voltage or tank circuit current is used. Calculate the heat loss by multiplying the power by the proportional coefficient, and use the capacitor voltage obtained from the voltage divider or the tank circuit current obtained from the current transformer to calculate the heat loss approximately to the square of the capacitor voltage or tank circuit current. Calculated from the equation that multiplies the proportional coefficient, and for the required effective heat output PN, -Pl-(!vOS
It is characterized by controlling the DC input island so that o+W: +1.

F Effect In the above configuration, various losses are made clear, and accurate DC input is applied in accordance with the required effective heat output. In addition, the voltage/current detection circuit has a simple configuration with one side common,
Prevent damage to the detection circuit and accidental personal injury due to high voltage.

G. Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 9.

FIG. 1 shows the power control system of a high-frequency heating device, in which a DC power supply 1 is composed of a commercial AC power supply 2 and a thyristor type converter 3, the converter 3 is adjusted by an automatic power regulator (APR) 4, and an oscillation circuit 5 This is to input DC power. Although the electron tube 6 is used as an oscillation element in the oscillation circuit 5, a semiconductor element may also be used.

7 is an automatic setting device, which calculates the required effective heat output value PN given from the required heat output calculator 8 and the operating performance %W of the oscillation element 6 given from the loss calculation type 9. A set value PSl:T for the automatic power regulator 4 is determined from the sc' electric circuit loss factor and the heat loss WH of the heated object 10.

Automatic power regulator 4 controls converter 3 so that deviation value PSET -Pl given from subtractor 11 becomes zero. Pl is the DC input of the oscillation circuit 5, and the DC input calculator 12 calculates Pi= from the DC voltage 4 and the DC current ■2.
Find it as 4・■2.

With the above control, p, ET=pN+w. ,,10w,
+wH, so DC human power Pi corresponding to the required effective heat output P8 should be input so that P, = p, -(WoS0+W, +WH). Figure 2 shows P, P, 4, Wo3oSW! :,
shows the relationship between w. -In addition, the required heat output calculator 8
By setting the conditions 13 such as the shape, dimensions, and material of the object to be heated 10, for example, a pipe (in this example, an electric resistance welded pipe),
As is known, the required heat output is automatically calculated.

14 is a manual setting word, and a switch 15 applies a setting value P9□ to the subtracter 11 instead of the automatic setting device 7.

The oscillation circuit g85 includes an electron tube 6, a tank circuit 16, grid positive feedback capacitors 17 and 18, a DC cut capacitor 19, a tink coil 2o for grid bias, a grid resistor 21, and a bypass capacitor 2.
It consists of 2. The Chirok coil 23 is for preventing high frequency current from flowing into the DC power supply 1.

Tank R116 has two capacitors cTl”TQ
and one coil T are connected in a π shape.

Coupling the coil 24 to the coil LT of the tank circuit 16,
A matching transformer 25 is used, and a heating element 2 is connected to this transformer 25.
The work coil is connected as 6.

In the oscillation circuit 5 of FIG. 1, a common ground line (common line) 27 of the circuit is used to detect various voltages and currents. That is, (1) In order to detect the DC voltage Ep applied to the oscillation circuit g85, the common wire 27 and the high voltage cotton 28
A voltage divider 2'9 is connected between the two.

(2) In addition, in order to detect the total DC current ■2 flowing through the 'lei oscillating circuit 5, the common! A shunt 30 is inserted into the part of the 11127 near the power supply.

(3) Furthermore, in order to detect the instantaneous operating voltage ep of the oscillation element 6, a voltage divider 31 is connected between the plate and the common line 27.

(4) Furthermore, the instantaneous operating current IP flowing through the oscillation element 6
In order to detect this, a high frequency current transformer (RFCT) 32 is installed between the cathode and the common line 27.

(5) Furthermore, in order to determine the electric circuit loss (■), a voltage divider 33 is connected between the terminals of the capacitor CTl of the tank circuit 16 (one terminal is the same as the common line 27), and the instantaneous capacitor voltage e is calculated.

This is to detect it. In addition, among the common wires 27, the capacitor C of the tank circuit 16 is connected to the capacitor C 8. A high frequency current transformer 34 is installed between C1□ and the tank circuit instantaneous current i
□ may be detected.

As described above, for example, by installing the resistor type voltage divider 29, 31゜33, shunt 30, and high frequency current transformer 32゜34 in the oscillation circuit 5, each can be configured with one side common while having the common grounding wire 27. This eliminates the need for insulation that would result in an ungrounded system, simplifying the structure. In particular, when detecting current in a high-voltage circuit, it is possible to prevent damage to the detection circuit due to insulation breakdown in the event of an abnormality, as well as accidental personal injury.

Next, the operating loss Wo9c1 of the DC input Pi1 oscillation element 6
Measurement of electric circuit loss W5 and heat loss WH will be explained.

[D Measurement of DC input P: From the DC voltage 4 (volts) detected by the voltage divider 29 and the DC current IP (ampere) detected by the shunt 30, P, = EP ・ IP (watts)...
It can be found as equation (1). The DC input calculator 12 calculates this.

Operation loss W of the oscillation element 6. Measurement of sc: Oscillation element 6
The instantaneous operating voltage ep (instantaneous plate voltage in this example)
and the instantaneous operating current ip (also the instantaneous plate current) each have a DC component and a high frequency component. eP.

By detecting ip with the voltage divider 31 and high frequency current transformer 32, the effective value ep(eff,) #1P(ef
f, ) to W. , o= eP(eff,) 1P(e
ff, ), and furthermore, it can be found as follows. The loss calculator 9 calculates this. The effective value is found as. However, T is a period.

OI Measurement of electric circuit loss: First, electric circuit loss consists of coil loss and transmission loss, and is the high frequency output P of the oscillation circuit 5 at no load (state where the heated object 10 is not coupled to the work coil 26). be equivalent to. Therefore, if the DC input at no-load time is Pll and the oscillation element operating loss at no-load time is W05o1, then w = p = p - w ...Formula (3)% Formula % On the other hand, electric circuit loss W6 is , effective value I of tank circuit current
It is proportional to T to the 1.8th power to the 2.2nd power. Therefore, when detecting the instantaneous capacitor voltage ec using the voltage divider 33, its effective value E. Therefore, the following formula (4) is obtained. However, K5 is a proportional coefficient and α is an index between 1.8 and 2.2, which are determined as described below. ω is the angular frequency, and C11 is the capacitance. Alternatively, when the instantaneous tank circuit current 1A is detected by the high-frequency current transformer 34, from its effective value I□, the equation (5) is obtained.

Therefore, multiple no-load high-frequency outputs PHFI are set using equation (3), and the effective capacitor voltage 4,
Alternatively, α can be determined by measuring the effective tank circuit current. That is, if both sides of equation (4) are taken as a lump, then pigeon P8.1 = bow α・-(ωq1~) ...Equation 6)
Then, by plotting the measured values on the rectangular coordinates of PHF1 and k(ω・ql・4) and applying a straight line approximation, α can be obtained from the slope of the straight line, and from the intercept of the straight line and the coordinate axis logPM, , can be obtained. It will be done.

Similarly, if both sides of equation (5) are taken as log, then PH
Fl=IRt4+αmari11...Equation 7)
Therefore, by plotting the measured values on the orthogonal coordinates of HFI and 7.II and performing a linear approximation, α can be obtained from the slope of the straight line, and 5 can be obtained from the intercept of the coordinate axis - PHFI.

Using 5 and α determined in this way, the loss calculator 9 calculates the electric circuit loss y under actual load using the above-mentioned equation (4) or equation (5).

Note that the value of α changes mainly depending on the conditions of the device, such as current, voltage waveforms, and circuit constants.

■ Measurement of heat loss: Heat loss is measured by using a dummy load, that is, a load that does not form a current-carrying circuit to the heated part.

That is, in an induction type high frequency heating device having a work coil 26 as shown in FIG. 3, a cut pipe is used as a dummy load 10D as shown in FIG.

When a dummy pipe IOD is coupled to the work coil 26, the electric power applied to the dummy pipe IOD is a heat loss WH, which is the sum of the outer circumferential pipe loss and the inner circumferential pipe loss.

Therefore, the heat loss W, is the high frequency output P8 at the time of dummy load.
The electric power is calculated by subtracting the electric circuit loss of 2 from 12.

凰-PHF2-凰2 In addition, PHF□ is the DC input P,2 at the time of a dummy load and the oscillation element operating loss W at that time. The difference is 9C2.

P=P-W HF2 12 09C2 Furthermore, the electric circuit loss Wl:2 is determined by the above equation (4) or equation (5). Therefore, v4 == p, -w. 5o2-w, ...Equation (8) On the other hand, the heat loss toughness is also proportional to the 1.8th power to the 2.2nd power of the effective value IT of the tank circuit current, similar to the electric circuit loss.

Therefore, when detecting the instantaneous capacitor voltage ec using the voltage divider 33, the above equation (4) W = K, · (ω
・C7, ・E. )β...Equation (9) Also, when detecting the tank circuit instantaneous current 11 by the high-frequency current transformer 34, 1, wH=, -1, β...Equation ill
becomes. However, to is a proportional coefficient, β is 1.8 to 2.2
is the index of

To select β, similarly to the selection of α in measuring electric circuit loss, multiple heat losses during dummy loads are set using equation (8), and the effective capacitor voltage 4 is set for each.
, or by measuring the effective tank circuit current IT and calculating the log value.

Using the mass β determined in this way, the equation (9
) or formula (depending on the field, the loss calculator 9 calculates the heat loss during actual load.

Note that the proportionality constant - depends on the specifications of the coil, the material of the workpiece 10, the molding dimensions, the wall thickness, and the like.

Based on the measurement method explained above in CI], OD, II, and N, with the pipe 10 as an object to be heated being pushed into the work coil 26 as shown in FIG.
Operating loss W0 of H oscillation element 6. . , electric circuit loss, and heat loss wind, and control the input on the DC input so that the effective heat output PN becomes PN = P: (W,: 10W), and the pipe 10 The V-shaped edge portions of the two are heated and melted and bonded.

In the above embodiment, an electron tube was used as the oscillation element 6, but
The same applies when using semiconductor elements.

In addition, although the cut pipe lOD shown in FIG. 4 without forming a current-carrying part was used to measure the loss using a dummy load, if the heated object 10 forms a current-carrying circuit as shown in FIG.
When forming the current-carrying circuit in the plate-shaped thing shown in Fig. 6 (al), in order to minimize the generation of heat and reduce the heating power, in the example shown in Fig. 5, a copper tube Cu is sandwiched between the plates. (Fig. 5 (b)), or in the example shown in Fig. 6, by placing copper pipes Cu in close contact with both sides of the plate and allowing water to pass through (Fig. 5 (b)).
Fig. 6 (bll) The effective heating power is suppressed to compensate for the load loss.

Further, in the above embodiment, an induction type device using the work coil 26 as a heating element has been described, but a contact type device having a contactor 35 shown in FIGS. 7 to 9 can also be used in the same manner as the induction type. Various power and losses can be determined. however,
In the case of the contact type, no current flows in the outer periphery of the pipe in either the pipe 1 or 1 gummy pipe IOD, so the heat loss wind is only the inner pipe loss.

Here, when explaining the calculations for power and loss measurement, both analog calculations and digital calculations are suitable. In the case of analog calculation, the calculation circuit can be integrated into an IC, resulting in lower cost. In the case of digital calculation, the output waveforms of various detectors (29 to 34) are stored for several minutes using a high-speed digital storage instrument, stored in digital memory via a multiplexer, and then the waveform data is transferred and calculated. Performed using a digital calculator.

Generally speaking, this type of digital calculation method is difficult to measure the voltage and current of an oscillation circuit because the higher the frequency, the more difficult it is to measure it.
The applicable oscillation circuit is 10KHz or more and 500KHz.
It can be assumed that the range is about k[h. Therefore, the number of waveform data stored in the digital memory is 500.
The half wavelength of klh is V2x 5001 &-= 10-'5
Since ec = 1000nsec, for example, 100
If a digital memory with a resolution of n5ee, preferably about 5°n5ee, is used, it will be sufficient to eliminate measurement errors.

■ As described in detail, according to the present invention, the required effective heat output can be precisely controlled, it can respond to changes caused by external disturbances, it can be controlled under unsteady operating conditions, and it is possible to eliminate waste. It has the advantage of being able to perform optimal and accurate heating and maintain product quality. In addition, since the detection circuit is common on one side, it has a simple configuration, and also detects voltage and current due to high voltage.
Road destruction and unforeseen personal accidents can be prevented.

[Brief explanation of the drawing]

1 to 9 show embodiments of the present invention; FIG. 1 is an overall control circuit diagram for control; FIG. 2 is a diagram showing the relationship between DC input, loss and effective heat output; and FIG. The figure is an explanatory diagram of the actual load state, Fig. 4 is an explanatory diagram of the dummy load state, and Fig. 5 (al,
(bl, Fig. 6(a). (bl is an explanatory diagram of the heating state of the actual load and dummy load in other examples, respectively, Fig. 7 is a perspective view showing heating of the dummy load in the case of contact type, Fig. 8 is The figure is an explanatory drawing of Fig. 7, and Fig. 9 is an explanatory drawing of the heating state of the edge part by the contact type.In the drawing, 1 is a DC LT source, 4 is an automatic power regulator (APR), and 5 is an oscillation circuit. , 6 is an oscillation element (electron tube), 7 is an automatic setting device, 8 is a required heat output calculator, 9 is a loss calculator, 10 is an object to be heated, 10D is a dummy load, 12 is a DC input calculator, 16 is a tank The circuit, q is its capacitor, 26 is a work coil, 27 is a common line 28 is a high voltage line, 29, 31, 33 are voltage dividers, 30 is a shunt, 32, 34 is a high frequency current transformer, 35 is a contactor .

Claims (1)

[Claims] The DC input P_i to the oscillation circuit is calculated by calculating the DC voltage obtained from a voltage divider connected between the high voltage line and the common line and the DC current obtained from a shunt inserted in the common line, The operating loss W_O_S_C of the oscillation element is calculated from the inter-element voltage obtained from the voltage divider and the current flowing through the element obtained from the current transformer installed between the oscillation element and the common line, and the electric circuit loss W_E is calculated from the tank. Using the capacitor voltage obtained from a voltage divider connected between the high voltage side terminal of the circuit capacitor and the common line, or the tank circuit current obtained from the current transformer attached to the common line part of the tank circuit, the capacitor voltage or tank circuit can be calculated. Calculate the heat loss W_H by multiplying the approximate square of the current by a proportional coefficient, and calculate the heat loss W_H by using the capacitor voltage obtained from the voltage divider or the tank circuit current obtained from the current transformer. Calculated from a formula that multiplies approximately the square of the proportional coefficient, and for the required effective heat output P_N,
_O_S_C+W_E+W_H) A high-frequency heating power control method characterized by controlling a DC input P_i so that