HK1261145B - High frequency power supply system with closely regulated output for heating a workpiece - Google Patents

Description

High-frequency power supply system with stable and regulated output for heating workpieces

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 62/270,952, filed December 22, 2015, the entire contents of which are incorporated herein by reference.

Field of the Invention

The present invention relates to a high frequency power supply system having a stable regulated output for heating one or more portions of a metal part as the portion or portions of the metal part are advanced.

Background Art

Induction welding is a form of welding that utilizes electromagnetic induction to heat one or more portions of a metal part as they are advanced. For example, heated portions of metal sheets, such as opposing edges, are welded together by applying force between the inductively heated portions in ambient atmosphere or a controlled environment, such as an inert gas or vacuum, for example, to form a tubular product.

Electric resistance welding (ERW) is a form of welding that uses electrical resistance heating to heat one or more sections of a metal part as they are advanced in an ambient atmosphere or controlled environment, such as an inert gas or vacuum, by applying a force between one or more resistively heated sections (e.g., opposing edges of metal sheets) to weld the heated surfaces together to form a tubular product.

High-frequency solid-state power supplies used in induction or resistance welding processes can also be used in other heating processes, such as induction annealing (heat treating) processes, where a metal workpiece or a region of a workpiece (such as a previously formed weld) requires heat treatment. The induction coil and the magnetically coupled heat-treating region of the workpiece form an electrical load circuit with dynamically changing load characteristics during the annealing process.

US Patent No. 5,902,506 (the '506 patent), the entire contents of which are incorporated herein by reference, discloses a high frequency forging welding or annealing power supply system using a variable reactor in a load matching device.

An object of the present invention is to provide a high frequency forging welding or annealing power supply system having an improved variable reactor that is superior to the high frequency power supply system disclosed in US Pat. No. 5,902,506 in providing a highly stable regulated output.

Summary of the Invention

In one aspect, the present invention is a high-frequency electric heating system for heating a portion or portions of one or more metal parts as the portion or portions of the metal parts are advanced, wherein the high-frequency electric heating system includes a solid-state inverter and a load matching and frequency control device, wherein paired variable inductors are used to achieve a closely regulated output from the high-frequency electric heating system to the load.

In another aspect, the present invention is a high-frequency variable inductor having a geometrically shaped movable insert core portion; a fixed split bus portion comprising: a complementary geometrically shaped split bus segment and a split bus electrical terminal for connecting the variable inductor to an electrical circuit, wherein the insert core portion can be moved into or out of the complementary geometrically shaped split bus segment to vary the inductance of the inductor pair.

The above and other aspects of the invention are described in this specification and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, as briefly summarized below, are provided for illustrative understanding of the present invention and do not limit the invention further described in the present specification and appended claims.

FIG. 1 is an example of a simplified diagram of a high-frequency heating power supply system of the present invention using a current source inverter.

FIG. 2 is an example of a simplified diagram of a high-frequency heating power supply system of the present invention using a voltage source inverter.

FIG3 is an example of a simplified diagram of a control system of the high-frequency heating power supply system of the present invention.

4( a ) and 4 ( b ) show examples of a pair of geometrically shaped conical varactors having a single solid or hollow conductive core insert of the present invention that can be used in a load matching arrangement of a high frequency power supply system of the present invention.

FIG4(c) is a detail of the load matching and frequency control apparatus shown in FIG1 or FIG2, showing that a pair of varactors in FIG4(a) and FIG4(b) is used for the reactor pair 32-33 in FIG1 and FIG2.

FIG. 5( a ) shows one example of a single geometrically shaped insert core formed of solid or hollow ferrite that may be used in the pair of varactors shown in FIG. 4( a ) and FIG. 4( b ).

FIG5(b) shows an example of a single geometrically shaped insert core formed of a ferrite rod array that can be used in the pair of reactors shown in FIG4(a) and FIG4(b).

FIG. 6 shows an example of a wedge-shaped high-frequency variable reactor of the present invention that can be used in a load matching device of a high-frequency power supply system of the present invention.

FIG. 7 shows an example of an elliptical parabola-shaped high-frequency variable reactor of the present invention that can be used in a load matching device of the high-frequency power supply system of the present invention.

8( a ) to 8 ( d ) show an example of a high-frequency variable reactor of the present invention, which includes a pair of conical two-turn variables that can be used in the load matching device of the high-frequency power supply system of the present invention.

Figures 9(a) and 9(b) show an example of a high-frequency variable inductor of the present invention, which includes a geometrically shaped pair of conical variable inductors with a single solid or hollow conductive core insert of the present invention, which can be used in the load matching and frequency control device of the present invention, wherein the separate electrical bus portions for each variable inductor in the inductor pair are connected together to form a single variable inductor.

FIG9(c) is a detail of the improved load matching and frequency control device shown in FIG1 or FIG2, showing that the high-frequency inductor of FIG9(a) and FIG9(b) can be used in a high-frequency power supply system.

DETAILED DESCRIPTION

In FIG1 , a rectifier 12 converts three-phase AC power to DC power and is connected to an inverter circuit comprising transistors 20 a, 20 b, 20 c, and 20 d via conductors 82 and 84 and a fixed inductor 18. The transistors may be metal oxide semiconductor field effect transistors or other suitable solid-state switching devices. A current sensor 16 provides an output proportional to the current supplied to the inverter and load 80. When the high-frequency power heating system of the present invention is used, for example, in an induction welding or annealing application or a resistance welding application, load 80 includes electrical leads and an induction coil or electrical contacts (contacting a portion or multiple portions) to be welded, annealed, or heated.

The inverter output wires 86 and 88 are connected to the load 80 through a load matching device 14, which includes: a first pair of variable inductors 32 and 33, each of which is electrically connected in series between each inverter output wire and the load 80; a second pair of variable inductors 34 and 35, each of which is electrically connected in parallel with the inverter output wire; a first (optional) high-frequency low-loss capacitor 36 connected in series between the inverter output wire and the load 80; and a second high-frequency low-loss capacitor 37 electrically connected in parallel with the inverter output wire, wherein all components are arranged in one embodiment of the present invention, as shown in Figure 1.

The load 80, the reactor pairs 32-33 and 34-35, and the capacitors 36 (if used) and 37 form a tank circuit connected to the inverter output conductors. Maximum power transfer is achieved when the inductive reactance and the capacitive reactance are equal. Selecting the values of capacitors 36 (if used) and 37 and the ranges of the two variable reactor pairs 32-33 and 34-35 begins with determining the nominal load inductance range, which is the sum of the nominal load inductance, any magnetic core (impeder) formed within the tubular article (if the heating process is induction welding), the auxiliary bus operating inductance, the range of load resistance matched to the welder in the welding application, and the welding frequency used for the welding application. It is also necessary to know the resistive impedance value at which the inverter can provide its full power. Based on this knowledge, the value of capacitor 37, Cp, is calculated as the value required to support the highest circulating current generated by the tank circuit at full power output. This can be shown as:

in:

π is equal to 3.1415926;

f is equal to the desired application frequency;

_R0 is equal to the resistive impedance required by the inverter to deliver its full power output, and

_Rmin is the minimum resistive impedance expected at the terminals of the working coil during the induction welding or annealing process.

Knowing _Cp , calculate the value _Cs of capacitor 36 (if used) so that the tank circuit resonates at the welding frequency in a welding application:

_Cs = ( _Cp · _Lnom ·(2·π·f) ^2-1 ) where:

L _nom is equal to the nominal load inductance.

With the values selected above, the circuit shown in FIG1 will provide the correct resistive impedance for the inverter and will therefore provide full power output when the work coil exhibits its nominal inductance and minimum resistance, and when the inductance of the two varactor pairs 32-33 and 34-35 is negligible (i.e., _Lp of reactor pair 34-35 is essentially infinite, and _Ls of reactor pair 32-33 has essentially zero inductance).

To match higher work coil resistance values in induction welding or annealing applications, the variable reactor pair 32-33 must be adjusted to achieve the current required to dissipate the same power as would be achieved with the minimum load resistance. This can be achieved by increasing the reactance value of the reactor pair 32-33, recognizing that if the load is matched, the voltage across the reactor pair 34-35 is constant at full power output. Since the load reactance is much higher than the resistance (high Q load), a good approximation is:

in:

Ls _(max) is the required maximum design value of the varactor pair 32-33, and

R _max is the maximum load resistance expected at the terminals of the load current supply means.

However, as _Ls increases to match the larger load resistance: the inductance of the tank circuit increases; its resonant frequency decreases; and thus the application frequency is reduced. To maintain the application frequency at its desired value, the reactance _Lp of the varactor pair 34-35 is reduced so that the effective inductance of the circuit is always equal to _Lnom :

L _p(min) =L _nom ·(L _nom ·L _s(max) ) ·L _s(max)

Therefore two variable reactor pairs are required, one with adjustable reactance from Lp _(min) to a large value and one with adjustable inductance from a small value to Ls _(max) . These reactor pairs are designed in such a way that their reactance can be adjusted when the inverter is delivering full power.

FIG2 schematically illustrates a voltage source tuned inverter connected to a load via a load matching device 14. Corresponding elements in FIG2 are denoted by the reference numerals used in FIG1. A filter capacitor 38 is also used, and the position of capacitor 36 relative to the other elements has been changed in FIG2. Capacitor 37 in FIG2 is optional for the voltage source inverter embodiment.

2 are essentially as described in conjunction with FIG1. Additionally, the varactors 32-33 and 34-35 are adjusted as described in conjunction with FIG1 with the goal of causing the load matching device 14 connected to the load 80 to resonate at the desired operating frequency.

The wires connecting the load current supply device (e.g., electrical contacts during resistance welding of a tubular article, or induction coils during induction welding or annealing of a tubular article) have an inductive reactance and resistance; the electrical contacts have an inductive reactance and resistance, and the induction coils have an inductive reactance and resistance. During resistance welding, the tubular article being formed presents an inductive reactance and resistance at the electrical contacts, and during induction welding or annealing, the reactance of the induction coil is affected by the material of the tubular article being formed or heated, which can vary along its length, as well as by the spacing between the induction coil and the tubular article. Therefore, as the tubular article is advanced, the impedance presented to the output of the load matching device typically varies, and it is necessary to compensate for this variation in order to maintain a substantially constant magnitude and frequency of the heating current.

FIG3 is a schematic block diagram of an automatic control apparatus which may be used with the apparatus shown in FIG1 to control the impedance of inverter 41 presented at its output leads 86 and 88 and thereby control the frequency and magnitude of the current supplied by inverter 41 .

Although not shown in FIG1 or FIG2, as shown in FIG3, the rectifier 12 may have a DC controller 43 for controlling the DC voltage output of the rectifier 12. As shown in FIG3, the nominal level of the rectifier output can be manually set. The output current from the current sensor 16 is provided to the current comparator 45, and the output of the comparator 45 is provided to the DC controller 43 to ensure that the maximum current level is not exceeded.

The output of current sensor 16 and the output of voltage and frequency sensor 47 (illustrated and selected to provide information about the voltage and frequency of power at conductors 86 and 88) are provided to comparator 49, which compares the measured voltage, current, and frequency with predetermined values for voltage, current, and frequency and acts as a load matching control for maintaining a desired load impedance and inverter frequency at the output of inverter 41. Comparator 49 provides electrical outputs that power actuators, such as motor M2 for varying the reactance control element of series reactor pair 32-33, and electrical outputs that power actuators, such as motor M1 for varying the reactance control of shunt reactor pair 34-35.

The output of the voltage and frequency sensor 47 is also provided to a high frequency controller 57 which controls and synchronizes the firing of the inverter transistors 20a to 20d.

In a preferred embodiment of the present invention, the normally controlled interval comparator 49 performs the following functions:

(1) measuring the voltage and the current, and if the ratio of the measured voltage to the maximum voltage and the ratio of the measured current to the maximum current are greater than a preset value (e.g., 1.05), the output of the comparator 49 operates the motor M2 to reduce the reactance of the reactor pair 32-33; if the resulting ratio is less than a preset value, such as 0.95, the output of the comparator 49 operates the motor M2 to increase the reactance of the reactor pair 32-33; and

(2) The measured frequency is compared with the expected frequency, and if the ratio of the measured frequency to the expected frequency is greater than a preset value, such as 1.05, the output of the comparator 49 causes the motor M1 to operate to increase the reactance of the inductor pair 34-35; if the ratio is less than a preset value, such as 0.95, the output of the comparator 49 causes the motor M1 to operate so as to reduce the reactance of the inductor pair 34-35.

Depending on the permissible variation in the desired load matching, the level of adjustment of the reactor pairs 32-33 and 34-35 may be different.

Load matching control or comparator 49, in conjunction with variable reactor pairs 32-33 and 34-35, controls the impedance presented by inverter 41 at conductors 86 and 88. Thus, reactor pair 34-35 controls the frequency at which inverter 41 operates, and reactor pair 32-33 controls the reactance in series with load 80, so that, together with reactor pair 34-35, the impedance presented by inverter 41 at output conductors 86 and 88 is equal or substantially equal, thereby maximizing the power supply at conductors 86 and 88. By using relatively low-loss capacitors 36 (if used) and 37, relatively low-loss reactor pairs 32-33 and 34-35, and relatively low-loss conductors between conductors 86 and 88 and load 80, maximum power will also be provided to load 80.

In the present invention, either or both of the reactor pairs 32-33 and 34-35 can be formed by a geometrically shaped pair of reactors having a single movable geometrically shaped insert core and a fixed separation bus, which in one embodiment of the present invention are made of conductive sheets (such as copper), for example, complementary conic sections, wedge-shaped (a polyhedron defined by two triangular and three trapezoidal faces) sections or parabolic conic sections as shown in Figures 4(a), 4(b), 6 or 7, respectively.

For example, in one embodiment of the present invention, FIG4(a) and FIG4(b) illustrate a variable inductor pair 60 in which a single short-circuited geometrically shaped insert core portion 62 serving as a reactance control element moves into or out of stationary and complementary geometrically shaped split conical bus portions 64a and 64b of a fixed split bus portion 64, as indicated by the double-headed arrows in FIG4(a) and FIG4(b), and the magnitude of the induced current in the insert core portion 62 establishes a variable magnetic flux field (also referred to as a variable energy field) from the alternating current in the complementary geometrically shaped split conical bus portions 64a and 64b of the fixed split bus portion 64, to A variable inductance is established for each of the pair of reactors at the split electrical bus terminal portions A1-B1 and A2-B2 of the AC bus, which can have a variable inductance range from a minimum inductance value when the geometrically shaped insert core portion 62 is fully inserted into the complementary geometrically shaped split conical bus portions 64a and 64b to a maximum inductance value when the geometrically shaped insert core portion 62 is withdrawn to a position (e.g., as shown in FIG4(a)), where the variable energy field in the interleaved space formed between the insert core portion 62 and the fixed split bus portion 64 is at a maximum value. FIG4(c) illustrates the pair of varactors 60 as the varactor pair 32-33 connected in the high-frequency power supply system of FIG1 or FIG2. Fixed split bus section 64 includes electrically insulated split conical bus sections 64a and 64b, as well as separated electrical terminal sections A2 and B2 (associated with conical bus section 64a) and separated electrical terminal sections A1 and B1 (associated with conical bus section 64b). That is, the electrically interconnected conical bus section 64a and the separated electrical bus terminal sections A2 and B2 are spatially separated from the electrically connected bus section 64b and the terminal sections A1 and B1.

The geometry of the magnetically interacting movable insert core portion and the fixed bus element is selected for a particular application based on the accuracy of the inductance variation that can be achieved using such a geometrically shaped inductor pair, which accuracy involves precise adjustment in the output frequency of the high-frequency power supply of the present invention, which is better than the accuracy obtained, for example, using the power supply of U.S. Patent No. 5,902,506.

Each geometrically shaped reactor pair includes a pair of reactors, such as the reactor pairs 32-33 and 34-35 in FIG1 or FIG2, which are adjustable in pairs as indicated by the dashed interconnection X in FIG1 or FIG2. For example, for the reactor pair 32-33, as shown in FIG4(a) and FIG4(b), the core portion 62 is inserted into or out of the geometrically shaped split bus portion of the fixed split bus portion 64 by utilizing an actuator (e.g., the motor M3 shown in FIG3 or the actuator M′ shown in FIG4(a) and FIG4(b)).

The designations of the AC buses (A1-B1) and (A2-B2) for the reactor pair 32-33 in Figures 1 and 2 are the same as those for the conical reactors in Figures 4(a) and 4(b).

FIG5(a) and FIG5(b) illustrate the use of magnetic material (e.g., ferrite 62a) for the conical core insert portion 62 of the conical reactor pair 60 in FIG4(a) and FIG4(b). In FIG5(a), the conical core insert portion 62a includes a solid or hollow core of magnetic material. In FIG5(b), the conical core insert portion 62b includes an array of ferrite rods forming the outer periphery of the core insert portion.

FIG6 shows another example of a high-frequency variable reactor 90 of the present invention that can be used with the high-frequency power supply system of the present invention.

The high-frequency variable reactor 90 includes a single short-circuit insert core section 92 of a polyhedral geometry defined by two triangular and three trapezoidal faces, which is identified herein by its common name as a wedge section, which moves into or out of the fixed and complementary geometrically shaped split wedge bus sections 94a and 94b of the fixed split bus section 94 as indicated by the double-headed arrow in FIG. 7 . The magnitude of the induced current in the insert core section 92 establishes a variable magnetic flux field (also referred to as a variable energy field) from the complementary geometrically shaped split wedge bus sections 94a and 94b of the fixed split bus section 94. The AC current is supplied to establish a variable inductance for each pair of reactors at the separated electrical bus terminal portions A1-B1 and A2-B2 of the AC bus, which can have a variable inductance range from a minimum inductance value when the geometrically shaped insert core portion 92 is fully inserted into the complementary geometrically shaped separated conical bus portions 94a and 94b to a maximum inductance value, with the minimum inductance value being when the geometrically shaped insert core portion 92 is fully inserted into the complementary geometrically shaped separated conical bus portions 94a and 94b, and the maximum inductance value being when the geometrically shaped insert core portion 92 is withdrawn to a position where the variable energy field in the interleaved space formed between the insert core portion 92 and the fixed separated bus portion 94 is at a maximum value. The variable reactor pair 90 is connected in the high-frequency power supply system shown in FIG. 1 or FIG. 2 as the variable reactor pair 32-33 and/or the variable reactor pair 34-35. Fixed split bus section 94 includes electrically isolated split wedge-shaped bus sections 94a and 94b, as well as separated electrical terminal sections A2 and B2 (associated with wedge-shaped bus section 94a) and separated electrical terminal sections A1 and B1 (associated with wedge-shaped bus section 94b). That is, bus section 94a and terminal sections A2 and B2 are electrically connected and spatially separated from bus section 94b and terminal sections A1 and B1.

FIG7 shows another example of a high-frequency variable reactor 110 of the present invention that can be used with the high-frequency power supply system of the present invention. The high-frequency variable reactor 110 includes a single short-circuit insert core section 112 of elliptical paraboloid geometry, which is moved inside or outside the fixed and complementary geometrically shaped elliptical paraboloid bus sections 114a and 114b of the fixed separated bus section 114 as shown by the double arrows in FIG7. The magnitude of the induced current in the insert core section 112 establishes a variable magnetic flux field (also called a variable energy field) from the AC current in the complementary geometrically shaped separated bus sections 114a and 114b of the fixed separated bus section 114, so that each pair of reactors is in AC. The separate electrical bus terminal sections A1-B1 and A2-B2 of the current bus establish a variable inductance that can have a variable inductance range from a minimum inductance value when the geometrically shaped insert core section 112 is fully inserted into the complementary geometrically shaped split conical bus sections 114a and 114b to a maximum inductance value when the geometrically shaped insert core section 112 is withdrawn to a position where the variable energy field in the interleaved space formed between the insert core section 112 and the fixed split bus section 114 is at a maximum. Varactor pair 110 is connected in the high-frequency power supply system shown in FIG. 1 or FIG. 2 as varactor pair 32-33 and/or varactor pair 34-35. Fixed split bus section 114 includes electrically isolated split conical bus sections 114a and 114b, as well as separated electrical terminal sections A2 and B2 (associated with elliptical paraboloid bus section 114a) and separated electrical terminal sections A1 and B1 (associated with elliptical paraboloid bus section 114b). That is, electrically connected bus section 114a and terminal sections A2 and B2 are spatially separated from electrically connected bus section 114b and terminal sections A1 and B1.

In other examples of the present invention, the geometrically shaped high-frequency reactor of the present invention may have other geometric forms, such as a pyramidal shape, depending on the variable inductance distribution required for a particular application, which is a function of the spacing of the geometrically shaped interleaved core portion and the fixed split bus portion. For example, in applications where a particular high-frequency variable reactor requires a linearly or logarithmically varying inductance to achieve heating using the high-frequency electric heating system of the present invention, a particular geometric shape may provide a more highly stable inductance distribution than another geometric shape.

FIG8 (a) to FIG8 (d) illustrate one embodiment of a high-frequency variable inductor 70 of the present invention that can be used with the high-frequency power supply system of the present invention. The high-frequency variable inductor 70 includes a pair of two-turn variable inductors 70, wherein the geometry is a conical section, and each inductor is paired, for example, the inductors 32 and 33 in FIG1 or FIG2, each having its own conical insert core section 72a and 72b, and its own conical two-turn separated bus section 74a and 74b. The first fixed separated bus section includes an electrically isolated separated conical bus section 74a and separated electrical terminal sections A1 and B1 (connected to the two-turn separated bus section 74a), and the second fixed separated bus section includes an electrically isolated two-turn separated bus section 74b and separated electrical terminal sections A2 and B2 (connected to the two-turn separated bus section 74b). This is the electrically connected two-turn separated bus section 74a, and the terminal sections A1 and B1 are spatially separated from the electrically connected two-turn separated bus section 74b and the terminal sections A2 and B2.

Figures 9(a) and 9(b) illustrate another example of a high-frequency variable inductor 120 of the present invention that can be used with the high-frequency power supply system of the present invention. The embodiment shown in Figures 9(a) and 9(b) is similar to that shown in Figures 4(a) and 4(b), except that the separated bus terminal portions A1 and A2 are electrically connected together at bus terminal A1′, and B1 and B2 are electrically connected together at bus terminal B1′, so that the pair of varactors forms a single inductor 120. In this embodiment, the inductor pair is configured as a single inductor 120 between buses A1′ and B1′, as shown in Figure 9(c), which in some embodiments of the present invention replaces the variable series inductor pair 32-33 with a single inductor 120. Similarly, by modifying the geometrically shaped inductor pair of the present invention shown in Figures 9(a) and 9(b), the other parallel inductor pairs 34-35 in Figures 1 or 2 can be replaced with a single inductor.

In some examples of the high frequency electric heating system of the present invention, an inductor having a fixed inductance value may be combined in series with any one or more variable inductors in the inductor pair of the present invention.

The movable insert core portion of each of the geometrically shaped pair of high-frequency variable inductors used in the present invention can be moved into and out of the geometrically shaped separated bus portion using a suitable actuator (for example, motor M1 or M2 for inductor pair 34-35 or 32-33, respectively, as shown in Figure 3), where the motor has, for example, a linear reversible output connection connected to the insert core portion, as shown by the dashed line diagram in the figure connected to the movable insert core portion and actuator M′.

The minimum required inductance of the application is determined by measuring the position of the movable insert core when the insert core is positioned within the geometrically shaped split bus portion. The maximum required inductance of the application is obtained when the movable insert core is fully inserted and withdrawn to a certain position to set the maximum inductance position of the insert core.

The heat of the geometrically shaped pair of high frequency varactors of the present invention can be dissipated by circulating a cooling medium, for example, in cooling tubes in thermal contact with the fixed split bus portion and/or the movable insert core portion.

In the foregoing description, for purposes of explanation, numerous specific requirements and numerous specific details have been set forth in order to provide a thorough understanding of the examples and embodiments. However, it will be apparent to one skilled in the art that one or more other examples or embodiments may be practiced without some of these specific details. The specific embodiments described are not intended to limit the invention but rather to illustrate it. The examples, figures, or descriptions thereof are provided to simplify the disclosure and aid in understanding the various inventive aspects.

For example, references throughout this specification to "one example or embodiment," "an example or embodiment," "one or more examples or embodiments," or "different examples or embodiments" mean that a particular feature can be included in the practice of the invention. In the description, various features are sometimes grouped together in one example, embodiment, figure, or description thereof to simplify the disclosure and aid in understanding the purpose of various inventive aspects.

The present invention has been described according to preferred examples and embodiments. Except for those explicitly indicated, equivalents, substitutions and modifications are possible and within the scope of the present invention. Those skilled in the art who have benefited from the teachings of this specification may modify it without departing from the scope of the present invention.

Claims (10)

1. A high-frequency electric heating system for heating one or more portions of a metal part as they are advanced, the high-frequency electric heating system comprising: A solid-state inverter having first and second inverter output leads for providing high-frequency electrical power, the magnitude and frequency of which depend on the impedance of a load connected to the solid-state inverter, the load including means for advancing a portion or more of the one or more metal parts while allowing an electrically heating current to flow through the portion or more of the one or more metal parts; and A load matching and frequency control device, connected to the output leads of the first and second inverters, and connected to the means for causing the electric heating current to flow in one or more parts of the one or more metal components, the load matching and frequency control device comprising: A first pair of variable reactors is connected in series in the output conductors of the first and second inverters and in the load, and a second pair of variable reactors is connected in parallel with the output conductors of the first and second inverters. When energized, the first pair of variable reactors and the second pair of variable reactors respectively generate a first pair of variable energy fields and a second pair of variable energy fields. The first pair of variable energy fields, the second pair of variable energy fields, and the first and second pairs of variable reactors are respectively made reactively variable by separate variable energy field changing devices adjacent to each of the first and second pairs of variable reactors and movable relative to each of the first and second pairs of variable reactors. At least one capacitor electrically connected to the first inverter output wire or the first and second inverter output wires and the load, wherein The first pair of variable reactors and the second pair of variable reactors each comprise a geometrically shaped reactor pair, the reactor pair comprising: Geometrically shaped movable insert core; Fixed discrete bus, which includes: A geometrically shaped discrete bus section having a geometrically complementary shape to a geometrically shaped movable insert core, providing an adjustable position for the geometrically shaped movable insert core to be inserted into the geometrically shaped discrete bus section, changing the inductance of the geometrically shaped reactor pair from a minimum inductance value to a maximum inductance value, having a minimum inductance value when the geometrically shaped movable insert core is fully inserted into the geometrically shaped discrete bus section, and having a maximum inductance value when the geometrically shaped movable insert core is withdrawn from the geometrically shaped discrete bus section to a certain position, at which the variable energy field in the staggered space formed between the geometrically shaped movable insert core and the geometrically shaped discrete bus section is at its maximum value; Separate electrical bus terminal section for electrically connecting each of the geometrically shaped reactor pairs in load matching and frequency control equipment; and An actuator, connected to a geometry-shaped movable insert core, is used to insert the geometry-shaped movable insert core into and withdraw it from the geometry-shaped separate bus section. 2. The high-frequency electric heating system according to claim 1, wherein the solid-state electric inverter is alternatively a voltage source tuned inverter, and the at least one capacitor is electrically connected in series with one of the first pair of variable reactors through one of the first and second inverter output lines, or a current source parallel inverter, and the at least one capacitor is electrically connected in parallel with the first and second inverter output lines. 3. The high-frequency electric heating system according to claim 2, wherein the voltage source tuned inverter has a second capacitor electrically connected in parallel with the output leads of the first and second inverters, and the first capacitor terminal of the second capacitor is electrically connected between the at least one capacitor and one of the first pair of variable reactors. 4. The high-frequency electric heating system according to any one of claims 1-3, wherein the geometrically shaped movable insert is formed of a short-circuited conductive material. 5. The high-frequency electric heating system according to claim 4, wherein the short-circuited conductive material may alternatively include a copper sheet or a solid copper insert. 6. The high-frequency electric heating system according to any one of claims 1-3, wherein the geometrically shaped movable insert core is alternatively formed of solid or hollow magnetic material. 7. The high-frequency electric heating system according to claim 6, wherein the solid or hollow magnetic material of the geometrically shaped movable insert core comprises ferrite or multiple ferrites. 8. The high-frequency electric heating system according to any one of claims 1-3, wherein the geometrically shaped movable insert core and the geometrically shaped separate bus segment are selected from the group consisting of a conical portion, a wedge-shaped portion, or a parabolic conical portion. 9. The high-frequency electric heating system according to any one of claims 1-3 further includes at least one fixed inductor connected in series with at least one of the first pair of variable reactors or the second pair of variable reactors. 10. The high-frequency electric heating system according to any one of claims 1-3, wherein the separate bus terminal portions of the first pair of variable reactors are connected together to electrically form a single series variable reactor connected in one of the first and second inverter output lines, and the separate bus terminal portions of the second pair of variable reactors are connected together to form a single parallel variable reactor connected in parallel with the first and second inverter output lines.