WO2016115514A1 - Alimentation électrique à induction résonante commandée par courant - Google Patents

Alimentation électrique à induction résonante commandée par courant Download PDF

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Publication number
WO2016115514A1
WO2016115514A1 PCT/US2016/013693 US2016013693W WO2016115514A1 WO 2016115514 A1 WO2016115514 A1 WO 2016115514A1 US 2016013693 W US2016013693 W US 2016013693W WO 2016115514 A1 WO2016115514 A1 WO 2016115514A1
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WO
WIPO (PCT)
Prior art keywords
inverter
rectifier
resonance
power supply
current
Prior art date
Application number
PCT/US2016/013693
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English (en)
Inventor
Oleg Fishman
Original Assignee
Oleg Fishman
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Oleg Fishman filed Critical Oleg Fishman
Publication of WO2016115514A1 publication Critical patent/WO2016115514A1/fr

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/06—Control, e.g. of temperature, of power

Definitions

  • the present invention relates generally to devices for induction heating and melting of magnetically coupled electrically conductive material inserted into an induction coil, and more particularly to current control series resonant power supplies and precise measurement of the power delivered into a magnetically coupled electrically conductive load.
  • Induction heating and melting of metals is a widely used process in metal parts production and treatment processes.
  • these processes including but not limited to forging, extrusion, welding, brazing, hardening, galvanizing, welding, and melting
  • the AC electric current in the induction coil induces eddy currents on the surface of a metal body placed inside the coil.
  • the power for heating is supplied from a variable frequency induction generator.
  • the coil reactance is compensated by a capacitor.
  • Two types of prior art induction power generators include series resonant voltage source inverters and parallel resonant current source inverters.
  • FIG. 1 A prior art series resonant voltage source generator is shown in Figure la.
  • An implementation of the voltage source generator is shown in Figure 3.
  • fixed voltage DC source 17 (Figure la) is implemented as a diode rectifier 31 ( Figure 3), the stiff DC voltage supported by the DC capacitor 18 ( Figure la) or 33 ( Figure 3).
  • the DC voltage is converted into AC via the inverter 16 ( Figure la), implemented as a four semiconductor bridge circuit 34 ( Figure 3).
  • the semiconductors may be of bipolar, IGBT, MOSFET, SiC- MOSFET type transistors or thyristors with anti-parallel diodes.
  • the AC output from the inverter is applied through an optional transformer 35 to a resonance loop 10 ( Figure 3) containing inductor 14 and capacitor 11 ( Figure 1) connected in series.
  • the resistance 12 represents the resistivity of the induction coil and resistance 15 represents the introduced resistivity of the heated load 13 as it is inserted into the coil. When the heated load is removed from inside the coil the resistance 15 has zero value and when the heated load is fully inserted into the coil, the resistance 15 has its maximum value.
  • the output power from the inverter may be given by:
  • I ac is the inverter current in the coil.
  • the series resonant circuit controls the output power by varying the frequency of the inverter.
  • the impedance of the resonant loop 10 is given by:
  • V out is the series the resonant voltage source inverter output voltage
  • the output power also can be measured as a vector product of the output voltage Vout and output current lout:
  • the output power of the series resonant voltage source inverter is varied by changing the inverter operating frequency
  • the frequency is changed around the resonance point or condition.
  • the operating frequency is changed by varying the frequency of control pulses applied to the gate terminals of the semiconductors.
  • Figure 2 illustrates a parallel resonant current source inverter 26 with fixed supply 28 while Figure 4 illustrates implementation of the parallel resonant current source inverter and supply.
  • the DC current is supported by the choke 27 ( Figure 2).
  • Fixed supply 28 may be implemented as a diode rectifier 41 ( Figure 4).
  • the bridge inverter 43 ( Figure 4) consists of four semiconductors that can be bipolar, IGBT, MOSFET, SiC MOSFET type transistors with in-line diodes.
  • the AC output from the inverter is applied through an optional transformer 44 ( Figure 4) to resonance loop 20 containing inductor 24 and capacitor 21 ( Figure 2) connected in parallel.
  • the resistance 22 represents the resistivity of induction coil and resistance 25 represents the introduced resistivity of the heated load 23 as it is moved into the coil.
  • resistance 25 represents the introduced resistivity of the heated load 23 as it is moved into the coil.
  • the output power of the parallel resonant current inverter is varied by changing the inverter operating frequency in a fashion similar to frequency variation of the series resonant inverter.
  • the magnitude of coil resistance 12 of the series resonant loop 10 ( Figure la) or magnitude of coil resistance 22 of the parallel resonant loop 20 ( Figure 2) are changing with frequency in the process of induction heating or melting. This change prevents accurate measurements or computation of the power lost in the coil and power delivered to the load in the induction heating process in prior art inverters.
  • this condition may require operating near or at resonance.
  • FIG. la is a simplified block diagram of one example of a prior art series resonant loop including a constant voltage AC power Source, heating coil, and conductive load.
  • FIG. lb is a chart of power vs. frequency series resonance in constant voltage series resonant inverter 16 of FIG. la.
  • FIG. 2 is a simplified block diagram of one example of a prior art parallel resonant loop with current source inverter, heating coil and conductive load.
  • FIG. 3 is a simplified schematic diagram of one example of a prior art constant voltage power source 30 with series resonant looplO.
  • FIG.4 is a simplified schematic diagram of one example of a prior art constant current source inverter 40 with parallel resonant loop 20.
  • FIG. 5 is a simplified block diagram of an exemplary embodiment of the present invention showing a current control series resonant power supply 50 with series resonant loop 10 comprised of series resonant capacitor 11, heating coil 12, and conductive load 13.
  • FIG. 6 is a simplified schematic diagram of one example of a current controlled resonant power supply with series resonant loop utilized in the present invention and one phase supply. - -
  • FIG 7 is a simplified schematic diagram of one example of a current controlled resonant power supply with series resonant loop utilized in the present invention and three phase supply.
  • FIG 7a is a simplified schematic diagram of one example of a current controlled resonant power supply with parallel resonant loop utilized in the present invention and three phase supply.
  • FIG. 8a is a simplified schematic diagram of one example of a resonance detection circuit configured in accordance with embodiments of the present invention.
  • FIG. 8b shows exemplary wave forms of the signals associated with the resonance detection circuit of FIG. 8a configured in accordance with embodiments of the present invention.
  • FIG. 9 shows exemplary input current waveforms and signals to control input current configured in accordance with embodiments of the present invention.
  • FIG. 10 is a simplified block diagram illustrating a power supply with dual AC output configured in accordance with embodiments of the present invention.
  • FIG. 11 is a simplified block diagram illustrating a power supply with multiple AC outputs and sectional coil configured in accordance with embodiments of the present invention. Summary of the Invention
  • a system and method for induction heating and melting of magnetically coupled electrically conductive material inserted into an induction coil, and particularly to current controlled series resonant power supply and precise measurement of the power delivered into a magnetically coupled electrically conductive load Additional embodiments of the present invention include concurrent operation of a number of inverters with multiple induction furnaces or with a sectional induction coil distributed along a single work piece to produce dispersed heating. Each of the coils can deliver to the work piece different power and achieve uneven heating according to a set pattern.
  • a current controlled resonant power supply with series resonant loop for example, as shown in Figure 5.
  • the power supply may comprise a variable voltage rectifier with line power factor correction (PFC) topology, step down voltage regulator, and voltage fed inverter.
  • the output of the inverter is connected through an optional transformer to a series resonant loop containing an induction coil and serially connected capacitor.
  • the electromagnetic field produced by the induction coil couples with the conductive load inserted into the coil inducing eddy current onto the load surface. This eddy current subsequently heats the load.
  • the amount of energy delivered to the load is monitored and controlled by a control circuit.
  • the control circuit is configured to a) adjust the inverter frequency to assure that the inverter always operates at resonance condition, b) adjusts the DC voltage across to the voltage fed inverter to assure that the delivered power to the inductive load is equal to a preset value.
  • a user interface device such as a touch screen may be utilized for user input and feedback/display purposes.
  • a resonance power supply for generating variable AC power to apply to an induction coil magnetically coupled to a work piece comprising: at least one rectifier (55) with power factor correction (PFC), at least one step down voltage regulator, at least one resonant inverter, at least one induction coil magnetically coupled with at least one work piece, and at least one control circuit configured to adjust at least one parameter associated with at least one of the rectifier and the resonant inverter responsive to the output of the resonant inverter.
  • PFC power factor correction
  • FIG. 5 there is shown a power supply 50 including variable voltage rectifier 55 with line power factor correction (PFC) topology, current controller labeled as step down voltage regulator 68, and voltage fed inverter 53.
  • the output of the inverter is connected through optional transformer 56 to a series resonant loop 10 comprised of capacitor 11 and induction coil 12.
  • the electromagnetic field produced by the induction coil 12 couples with a conductive load 13 inserted into the coil inducing eddy current onto the load surface. This eddy current subsequently heats the load.
  • the frequency of the inverter is not changed to adjust the power per formula (4), but maintained relatively constant at resonant frequency w 0 per formula (6).
  • the output power P out is changed by varying the inverter voltage V out per formula (4)..
  • control circuit 52 the amount of energy delivered to the load is carefully monitored and controlled by control circuit 52.
  • This circuit a) -assures that the inverter always operate at resonance condition according to formulas (7), (8), (9); b) adjusts the DC voltage supplied to the voltage fed inverter to assure that the delivered power to the inductive load is equal to a preset value.
  • the touch screen 51 serves as a user interface device.
  • the operator may monitor the process parameters such as but not limited to - - inverter output power P out , power delivered to the load Pi oa d , inverter frequency w, inverter current I aCi inverter output voltage V out , line voltage Vii ne , the DC voltage applied to inverter in v _DC, as well as calculated value of inverter efficiency Pi oa d pout .
  • the operator may set process parameters for power delivered to the load ( work-piece) Po.
  • the induction loop 10 operates at the resonance frequency condition (formula (8))
  • the inductive impedance 14 shown e.g. in FIG.
  • the circuit control is configured such that the inerter voltage is adjusted to generate a preset value of power into inductive load 13.
  • the frequency of the inverter 53 (in FIG. 5; 70 in FIG. 6) current does not significantly change in the process of induction heating and therefore the coil resistance does not change.
  • the system and method of the present invention leverages this to enable separate computation of the power losses in the induction coil and power delivered to the work-piece.
  • the system is configured to control the input power factor correction (PFC) rectifier- regulator in a way that input line current is always in phase with the input line voltage and has a sine wave shape with low line total harmonic distortions (THD).
  • PFC input power factor correction
  • FIG. 6 is a simplified one line of a single phase step down voltage regulator resonant power supply 60 according to an embodiment of the invention.
  • the circuit comprises a PFC rectifier shown in Figure 5 as element 55 and labeled in Figure 6 as 65 with step-up voltage regulation, step-down voltage regulator 68, series resonant inverter 70 (labeled as 53 in Figure 5), and resonance induction loop 10 with optional transformer 35.
  • the full bridge inverter 70 consists of four semiconductor switches 73 that could be bipolar, IGBT, MOSFET, SiC
  • MOSFET transistors 71 or thyristor type with anti-parallel diodes by way of example. Pairs of switches diagonally across the inverter bridge A-B and C-D are turning on/off periodically with frequency( w 0 ). When this frequency is equal to the resonance frequency the inverter voltage V ou t will be in phase with inverter current I ac per formula (9).
  • Figure 8a shows non-limiting elements of the control circuit 52 (FIG. 5) that can be used for detection of the resonance.
  • the sine wave signal representing inverter current I ac passed through the comparator 75 produces pulses 77( Figure 8b) synchronous with the inverter current.
  • Another set of pulses 78 is synchronous with the inverter voltage. Both strings of pulses are compared on a XOR circuit 76 which generates the difference pulses 79.
  • Figure 8b shows, when the inverter operates below resonance (w ⁇ w 0 ) the inverter current signal pulses 77 are leading the inverter voltage signal pulses 78. Conversely when the inverter operates below resonance (w> w 0 ) the inverter current signal pulses 77 are lagging the inverter voltage signal pulses 78. In resonance condition the current pulses 77 are totally in phase with the voltage pulses 79 and the XOR pulses' duration are near zero. The objective of the inverter frequency control is to minimize the duration of the XOR pulses.
  • the step-down voltage regulator such as shown by element 68 in Figure 6 regulates the DC voltage across series resonant inverter 70, in the range below the PFC regulator voltage.
  • the step down voltage regulator 68 includes capacitor 72, inductor 66, semiconductor switch 69 , and diode 67.
  • the switch 64 is periodically tumed off for duration t each interval T. During these "off periods the current is not supplied from the PFC rectifier 65 and circulates via diode 67. As a result the voltage on the capacitor 72 voltage is reduced to:
  • V inv _ D c V pfc * t /T (10)
  • V PfC is the DC voltage on the output of the PFC rectifier.
  • the voltage Vi nv _DC in eq. (10) has about the same value as to Vi nv _ out in eq. (4).
  • the step-down voltage regulator is activated only when the DC voltage across the inverter(s) must be reduced below the minimum voltage achievable by the PFC rectifier 65 equal to .
  • the transistor switch 69 is conducting continuously and the voltage on capacitor 72 is regulated by the PFC rectifier 65.
  • the PFC rectifier with step up voltage regulation capability 65 comprises line inductors 61, diode rectifier bridge 62, decoupling diode 63, and DC capacitor 75.
  • the PFC rectifier serves a double purpose: a) when required, to generate a voltage higher than - -
  • the elevated voltage is produced by periodically turning on transistor switch 64 for duration t var each interval T var . Both the values of t var and T var change during the input line voltage period ⁇ 11 ⁇ according to a PFC control algorithm and illustrated in figure 9.
  • the switch 64 When the switch 64 is closed the line voltage is applied to the line inductors 61, the diode bridge 62, and switch 64. The current builds-up in the inductors 61 and the reactive energy stored in the inductor increases. When switch 64 opens, the current in the inductor continues to flow via diode 63 into capacitor 75 and the stored energy flows into the capacitor, charging it to the voltage which magnitude may be larger than the input line voltage.
  • FIG. 9 The principle of the PFC control algorithm is shown in Figure 9 which is referred to as "bang-bang" control
  • the value of the desired or target line sine wave current 91 is computed based on the current consumption of the resonant loop.
  • the signal 95 is proportional to the rectified line voltage.
  • Controller circuitry implemented in one or more hardware and/or software modules such as voltage and/or current transformers for monitoring and or adjusting one or more of current, voltage, and power, may be utilized for performing the functionality described herein.
  • the "bang- bang” algorithm operates as follows: when the current in inductors 61 reaches the signal SI the transistor 64 is turned on, and the instantaneous current increases as illustrated in Figure 9. When the current in inductors 61 reaches the signal S2 the transistor 64 is turned off, and the instantaneous current decreases. In this way the current maintains sine wave form with a small saw-tooth ripple (93, 94).
  • the string of pulses 97 is applied to the control gate of transistor 64 to cause the saw tooth current in the inductors 61.
  • FIG. 7 is a simplified diagram of a three phase current controlled resonant power supply 70 with series resonant loop 10.
  • the PFC rectifier/regulator contains three inductors connected to line phases A, B, and C. It also contains three diode bridges 62, three semiconductor switches 54 and three sets of decoupling diodes 63. It also includes three PFC controls, each synchronized with voltages A, B, and C and operating as shown on Figure 9.
  • Embodiments of the present invention allow for accurate monitoring of the power delivered into the work-piece inserted into induction coil. When the coil is empty the control can register the power dissipated on the coil:
  • control may register the total output power P out in accordance with expression (5).
  • the power delivered into the work piece is equal to:
  • Pioad Pout - N 2 *I ac 2 * R 12 (13) where Pi oa d is used as a control variable in the control circuit.
  • FIG. 7a is a simplified one line of a three phase current controlled resonant power supply 70 with parallel resonant loop 20.
  • This circuit is very similar to the circuit shown in Figure 7, however, the resonant capacitor 11 is connected in parallel with inductor 14 rather than in series as shown in FIG.7.
  • the power supply shown in Figure 10 presents a non-limiting block diagram of a power supply 100, comprising one of PFC rectifier/regulator 55, and a pair of inverters 53A and 53B each controlled by a step-down voltage regulator 68A and 68B.
  • Each inverter generates induction current in coils 14A and 14B, heating induction loads 13A and 13B, respectively.
  • the power supply is with a pair of induction melting furnaces for sequential processing. This power supply may be comprised of more than two inverters and step- down voltage regulators.
  • FIG. 11 presents a non-limiting block diagram of a power supply 110, comprising a PFC rectifier/regulator coupled to a number of step-down voltage regulators 68A-68D and inverters 53A- 53D, each connected to a section (14A-14D) of a multi-section coil. All the inverters operate at the same frequency, however, at different set power levels. Due to the equal frequency - - operation there is very little magnetic interruption between the coils, thereby ensuring a smooth transition between heating zones.
  • a resonance power supply for generating variable AC power to apply to an induction coil magnetically coupled to a work piece.
  • the supply includes at least one rectifier (55/65) with power factor correction (PFC); at least one step down voltage regulator (68) having an input coupled to the at least one rectifier, at least one resonant inverter (70) having an input coupled to the at least one step down voltage regulator, at least one induction coil (14) magnetically coupled to at least one work piece (13), and at least one control circuit (52; FIG.
  • the at least one step down voltage regulator is operative to regulate the DC voltage across resonance inverter when the voltage at the input of the current regulator exceeds a voltage threshold for supplying a set power level to the at least one induction coil.
  • the at least one rectifier with PFC converts AC line current into DC current, such that the shape and phase of the line current follows the shape of the line voltage.
  • the rectifier with PFC is a one phase rectifier.
  • the rectifier with PFC is a three phase rectifier.
  • the at least one control circuit includes controller circuitry for bang-bang control of the rectifier with PFC. In an embodiment, the at least one control circuit includes controller circuitry for voltage control across the resonant inverter according to an output of the step down voltage regulator. In an embodiment, the at least one control circuit includes controller circuitry for frequency control of at least one resonance inverter. In an embodiment, the at least one control circuit includes controller circuitry for monitoring power applied to the at least one induction coil and work piece, computing power losses in induction coil, and computing power applied to the work piece.
  • a method of generating variable AC power to apply to induction coil to heat a magnetically coupled work piece comprising: generating an input power factor correction (PFC) via at least one rectifier; generating AC power on an induction coil from at least one resonant inverter; controlling DC voltage across the at least one resonant inverter using at least one step down voltage regulator; using at least one induction coil to magnetically couple with at least one work piece, and controlling the inverter and the PFC of the at least one rectifier according to the output of the inverter to operate the at least one inverter at resonance frequency.
  • PFC input power factor correction
  • the method further comprises controlling via at least one step down voltage regulator, the amount of DC current to the at least one resonant inverter to set a power level in the at least one work piece.
  • the method further comprises - - converting in the at least one rectifier with power factor correction AC line current into DC current to cause shape and phase of the line current to follow the shape of line voltage.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Inverter Devices (AREA)
  • General Induction Heating (AREA)

Abstract

La présente invention concerne une alimentation électrique à résonance permettant de générer un courant alternatif variable à appliquer à une bobine d'induction accouplée magnétiquement à une pièce à travailler comprenant : au moins un redresseur de courant (55) avec correction du facteur de puissance (PFC), au moins un régulateur de tension abaisseur (68), au moins un onduleur résonant (53), au moins une bobine d'induction couplée magnétiquement avec au moins une pièce à travailler (13), et au moins un circuit de commande (52) conçu pour régler au moins un paramètre associé au redresseur et/ou à l'onduleur résonant en réponse à la sortie de l'onduleur résonant.
PCT/US2016/013693 2015-01-16 2016-01-15 Alimentation électrique à induction résonante commandée par courant WO2016115514A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US201562104313P 2015-01-16 2015-01-16
US62/104,313 2015-01-16
US201562142547P 2015-04-03 2015-04-03
US62/142,547 2015-04-03

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018050550A1 (fr) * 2016-09-13 2018-03-22 Ralph Meichtry Procédé et dispositif de débosselage
CN109804713A (zh) * 2016-10-25 2019-05-24 伊莱克斯家用电器股份公司 用于校准感应灶具的功率控制回路的方法
WO2023043385A3 (fr) * 2021-09-15 2023-06-29 Mamur Teknoloji Sistemleri San. A.S. Procédé de commande de circuit de puissance et de circuit de commande pour une plaque de cuisson à induction

Citations (5)

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Publication number Priority date Publication date Assignee Title
US20090314768A1 (en) * 2005-06-01 2009-12-24 Inductotherm Corp. Gradient Induction Heating of a Workpiece
JP2010033923A (ja) * 2008-07-30 2010-02-12 Mitsui Eng & Shipbuild Co Ltd 誘導加熱方法、および誘導加熱装置
US20130194851A1 (en) * 2012-01-31 2013-08-01 General Electric Company Phase angle detection in an inverter
US20130248520A1 (en) * 2010-12-03 2013-09-26 Mitsui Engineering & Shipbuilding Co., Ltd. Induction heating device, induction heating method, and program
US20140008356A1 (en) * 2011-03-23 2014-01-09 Mitsui Engineering & Shipbuilding Co., Ltd. Induction heating device, control method thereof, and control program thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090314768A1 (en) * 2005-06-01 2009-12-24 Inductotherm Corp. Gradient Induction Heating of a Workpiece
JP2010033923A (ja) * 2008-07-30 2010-02-12 Mitsui Eng & Shipbuild Co Ltd 誘導加熱方法、および誘導加熱装置
US20130248520A1 (en) * 2010-12-03 2013-09-26 Mitsui Engineering & Shipbuilding Co., Ltd. Induction heating device, induction heating method, and program
US20140008356A1 (en) * 2011-03-23 2014-01-09 Mitsui Engineering & Shipbuilding Co., Ltd. Induction heating device, control method thereof, and control program thereof
US20130194851A1 (en) * 2012-01-31 2013-08-01 General Electric Company Phase angle detection in an inverter

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018050550A1 (fr) * 2016-09-13 2018-03-22 Ralph Meichtry Procédé et dispositif de débosselage
CN109997412A (zh) * 2016-09-13 2019-07-09 R·梅切特利 去除凹痕的方法和设备
CN109997412B (zh) * 2016-09-13 2022-02-08 R·梅切特利 在片状金属结构中引起局部加热的方法、设备和工作头
CN109804713A (zh) * 2016-10-25 2019-05-24 伊莱克斯家用电器股份公司 用于校准感应灶具的功率控制回路的方法
WO2023043385A3 (fr) * 2021-09-15 2023-06-29 Mamur Teknoloji Sistemleri San. A.S. Procédé de commande de circuit de puissance et de circuit de commande pour une plaque de cuisson à induction

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