GB2518634A - Induction heater circuit protection closed loop control process - Google Patents

Induction heater circuit protection closed loop control process Download PDF

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Publication number
GB2518634A
GB2518634A GB1317083.2A GB201317083A GB2518634A GB 2518634 A GB2518634 A GB 2518634A GB 201317083 A GB201317083 A GB 201317083A GB 2518634 A GB2518634 A GB 2518634A
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GB
United Kingdom
Prior art keywords
induction heater
subsystem
feedback
hfacg
control process
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Legal status (The legal status 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 status listed.)
Withdrawn
Application number
GB1317083.2A
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GB201317083D0 (en
Inventor
Gary John Milton
William Law
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
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Publication date
Application filed by Individual filed Critical Individual
Priority to GB1317083.2A priority Critical patent/GB2518634A/en
Publication of GB201317083D0 publication Critical patent/GB201317083D0/en
Publication of GB2518634A publication Critical patent/GB2518634A/en
Withdrawn legal-status Critical Current

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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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/122—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/122—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters
    • H02H7/1227—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters responsive to abnormalities in the output circuit, e.g. short circuit
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/005—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection avoiding undesired transient conditions
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Induction Heating (AREA)
  • Fixing For Electrophotography (AREA)

Abstract

A closed loop protection system for an induction heater responds to detection of: voltage spikes in, an oscillation frequency characteristic of, rapid surges in power supply current drawn by, and excess power supply current drawn by a high frequency generator of the heater system; and in response to detecting any of these sends feedback to a control subsystem to limit voltage or current of the generator. The closed-loop control process can protect the induction heater circuits using actions including: temporary shut-down, fast active limiting of supply current and fast active limiting of internal high voltages, in dependence on the abnormal circuit conditions that arise and are detected. The protective actions are effected before the abnormal circuit conditions can develop to damaging levels and can also alert the user to the existence of an abnormal condition, by an indicator device or by affecting the behaviour of the induction heater, so that action can be taken to deal with the originating problem.

Description

Induction heater circuit protection closed loop control process
Field of invention
This invention relates to a device which uses electromagnetic induction, to heat electrically conducting objects. The invention helps to protect from damage the electronic circuits of such induction heater systems in the event of occurrence of certain types of electrical fault conditions, by using single and multiple closed-control loops.
Background of invention
Induction heating is the process of heating an electrically conducting object (usually but not exclusively a ferrous metal) by electromagnetic induction, where eddy currents (also called Foucault currents) are induced within the metal with the consequent resistive losses leading to Joule heating of the metal. An induction heater (for any process) consists of an electromagnet, through which a high-frequency alternating current (Ac) is passed. Heat may also be generated by magnetic hysteresis losses in materials that have significant relative permeability. The frequency of AC generated depends on the object size, material type, coupling (between the inductive loop (coil) and the object to be heated) and the penetration depth. Induction heaters can provide a solution of heating electrically conducting objects for the purposes of heat manipulation and/or shape/size expansion.
Induction heaters need an electronic driving circuit system that generates the high power high frequency alternating current required to energise the induction loop (coil) and the associated alternating magnetic field, to thereby provide the power to inductively heat the intended conductive object. This High Frequency Alternating Current Generation ("HFACG") subsystem, requires controls and a suitable power supply in order to function properly, safely and reliably within sustainable limits of stress to its components.
The circuit of the HFACG subsystem can be damaged by the electrical or thermal stresses of: operating with excess supply voltage; drawing prolonged excess current due to inappropriate loading of the said subsystem's output; operating in an inappropriate mode or frequency range; surges in the supply current drawn due to occurrence of output loading faults; voltage spikes generated in the said circuit due to occurrence of output loading faults; current surges and voltage spikes incident upon the induction heater via the external power supply connection (e.g. via AC mains connection).
Current surges and voltage spikes can occur as a result of a loading fault wherein the output inductive loop (coil) is short-circuited, either directly or via an electrical arc: the voltage spike arises as a consequence of interruption of a surge consequent on the increased electrical load.
Similarly, current surges and voltage spikes also can occur as a result of a loading fault wherein the output inductive loop (coil) connection is suddenly interrupted completely or caused to arc: the voltage spike arises as a consequence of interruption of the current, particularly after of a surge consequent on the increased electrical load from the power losses in the arc.
Dependent on the design of the induction heater, there can occur an inappropriate loading condition wherein the inductive loop (coil) is of unsuitable design or is not connected. The high frequency circuitry of the induction heater is generally designed to operate within a particular frequency range where its operation is both efficient with minimised losses and in a mode that does not impose excessive stresses on its components. An inappropriate loading condition can cause operation outside the intended frequency range with as a consequence potentially higher losses, higher stresses, higher voltages or higher currents.
Statement of invention
Illustrative embodiments of the present invention meet the above noted need by providing an induction heater with a closed-loop control process to protect the induction heater circuits against primarily the effects of two types of fault condition: (1) loading faults (as presented to the output of the said induction heater's High Frequency Alternating Current ("HFACG") subsystem) and (2) inappropriate loading conditions (as presented to the output of the said induction heater's HFACG subsystem).
Loading faults include the short-circuiting of the output induction loop (coil) of the induction heater and interruption of the circuit path formed by the said output induction loop (coil). Inappropriate loading conditions include the said output induction loop (coil) being of unsuitable design or not being connected.
The closed-loop control process protects the induction heater by effecting various of certain actions: shutting down the HFACG subsystem of the said induction heater; limiting power supply current surges into the said HFACG subsystem; limiting voltage spikes within the said HFACG subsystem.
The said closed loop control process actions are in response to feedback concerning the states of: the power supply current to the said HFACG subsystem; peak voltages within the said HFACG subsystem; the prevailing oscillation frequency of the said HFACG subsystem.
The said closed loop control process action of shutting down the said HFACG subsystem is effected by turning off the power supply feed to the said HFACG subsystem. The shut-down so effected is for some predetermined period, dependent on the various aspects of the feedback. The said action of shutting-down entails a time delay between the advent of a state that would trigger the said action and the completion of the said action.
The said closed loop control process action of limiting power supply current surges into the said HFACG subsystem is effected by active reduction of the voltage of the power supply feed to the said H FACG subsystem, in accordance with the feedback concerning the magnitude of the said power supply current, to the point where the said power supply current is limited to a predetermined threshold value. The control loop in respect of this control loop process action is fast-acting.
The said closed loop control process action of limiting voltage spikes within the said F-IFACG subsystem is effected by turning on a current sink, in accordance with the feedback concerning the magnitude of the said spike voltage in the said HFACG subsystem, to sink current from within the said HFACG subsystem and thereby to partially de-energise the said HFACG subsystem and prevent the spike voltage from rising. The control loop in respect of this control loop process action is fast-acting.
Both the said closed loop control process actions of (1) limiting power supply current surges into the said HFACG subsystem and (2) limiting voltage spikes within the said HFACG subsystem are fast-acting, and neither can be sustained for an extended period of time due to the high levels of power 3( dissipation that they each entail. In a preferred embodiment of the invention, either of these two said actions is only ever effected in conjunction with effecting an action to shut down the said HFACG subsystem, as may be required in order to safely limit temporary phenomena.
The feedback concerning the state of the power supply current to the said HFACG subsystem has two aspects: (1) fast acting current detection and (2) precise detection of current. These two said aspects are described in the following paragraphs.
The fast-acting current detection feedback concerns the magnitude of the power-supply current into the said HFCAG subsystem. If this said power-supply current exceeds a predetermined maximum value for surges, then the control process will effect two actions: (1) shutting down the said HFACG subsystem of the said induction heater and (2) limiting the power supply current (surge) into the said HFACG subsystem. Thus an event that causes a surge in the said power supply current will be dealt with by safely limiting the said power supply current while shutting down the said HFACG subsystem.
The feedback from the precise detection of current also concerns the magnitude of the power- supply current into the said HECAG subsystem. If this said power-supply current exceeds a precisely-predetermined maximum value for normal operation (which is lower than the maximum value for surges), then the control process will effect a single action: shutting down the HFACG subsystem of the said induction heater.
The feedback concerning the state of peak voltages within the said HFACG subsystem is so arranged that if a voltage is detected that exceeds the apparent normal operating maximum voltage by a predetermined margin, then the control process will effect two actions: (1) shutting down the said HFACG subsystem of the said induction heater and (2) limiting the voltage (spike) within the said HFACG subsystem. Thus an event that causes a voltage spike within the said HFACG subsystem will be dealt with by safely limiting the said voltage spike while shutting down the said HFACG subsystem.
The feedback concerning the state of the prevailing oscillation frequency of the said HFACG subsystem is so arranged that if the said oscillation frequency is outside of the predetermined operational oscillation frequency range of the induction heater system, then the control process will effect a single action: shutting down the HFACG subsystem of the said induction heater.
The shut-down effected by the said closed loop control process may be arranged to persist for some arbitrary predetermined time in dependence on the various aspects of the feedback and so be arranged to reduce the duty cycle of the induction heater to: avoid immediate further recurrence of the effects of a given fault condition on the operation of the HFACG subsystem; mitigate stress upon the circuit of HFACG subsystem and the other circuits of the induction heater system; and through the consequent effect on the behaviour of the said induction heater system to indicate to the user of the said induction heater system that a fault condition is in existence in respect of the said induction heater system, so that appropriate corrective actions or other actions may be taken by the user.
The control process within the induction heater can also be arranged to operate an indicator device or devices in dependence on the various aspects of the feedback to indicate to the user of the said induction heater system that a one or more fault conditions is in existence in respect of the said induction heater system, so that appropriate corrective actions or other actions may be taken by the user. 4(
Brief description of drawings
The invention will now be described solely by way of example and with reference, with the accompanying drawing.
Fig.1 induction heater system; Fig.1 (100) Voltage in: this is the power input to the induction heating system, for example AC mains; Fig.1 (101) Rectification: the conversion of alternating external power supply current into direct current for the internal power supply; Fig.1 (102) control: this subsystem controls the power-supply to the High Frequency AC Generation and provides fast limiting of voltage spikes in the High Frequency AC Generation by actively sinking current as necessary from points within the High Frequency AC Generation circuit.
Fig.1 (103) Fast acting detection of current: which comprises means to detect, according to predetermined criteria, rapid surges in the power supply current drawn by the High Frequency AC Generation subsystem of the said induction heater, and send a feedback signal or feedback signals to the control subsystem for rapid response; Fig.1 (104) Precise detection of current: which comprises means to detect, according to precise predetermined criteria, excess power supply current drawn by the High Frequency AC Generation subsystem of the said induction heater, and send a feedback signal or feedback signals to the said control subsystem; Fig.1 (105) Voltage spike detection: which has means to detect, according to predetermined criteria, voltage spikes in the High FrequencyACGeneration subsystem of the said induction heateç and send a feedback signal or feedback signals to the said control subsystem for rapid response; Fig.1 (106) Detection of abnormal frequency: which comprises means to detect predetermined specified characteristics in the frequency of oscillation in the High Frequency AC Generation subsystem of the said induction heater, and send a feedback signal or feedback signals to the said control subsystem; Fig.1 (107) High frequency A.C generation: this subsystem, when provided with DC power and controlled accordingly, generates the high power, high frequency alternating current required to energise the induction loop (coil) sufficiently for the intended level of heating capability; Fig.1 (108) induction loop (coil); this, when energised, creates a region of intense high frequency alternating magnetic field capable of inducing strong eddy currents in a conductor placed within the said region.
Details In Fig.1 the block diagram describes the function flow of the induction heater closed-loop regulation control. Starting with block (100), power is supplied to the induction heater device (Fig 1). The Alternating current power (100) is then rectified to direct current by the rectification (101).
The direct current power feed from the rectification (101) to the high frequency A.C generation ("HFACG') subsystem (107) passes via the control subsystem (102) which under normal operation allows the feed to pass through, but in dependence on the feedback from the various monitoring (detection) subsystems (103, 104, 105 and 106) either or both inhibits/alters the power feed to the high frequency HFACG subsystem (107).
The HFACG subsystem (107) in combination with an induction loop (coil) (108) will produce a sinusoidal output voltage and current, at the frequency of resonance of the combination. The control (102) is regulated by a closed -looped control system which will either/or inhibit and alter the output/input of (102) based on the feedback information detected from (103, 104, 105, 106).
Fast acting detection of current (103) monitors output from the control subsystem (102) within the induction heater system (Fig 1). If the power-supply current passing through the control subsystem (102) to the HFCAG subsystem (107) exceeds a predetermined maximum value for surges, feedback from the fast acting detection of current (103) to the control subsystem (102) causes the control subsystem (102) to act rapidly to reduce the said power supply current to the said predetermined value and thereby to exert a fast-limiting action on the said power supply current.
The precise detection of current (106) monitors output from the control subsystem (102) within the induction heater system (Fig 1). If the power-supply current passing through the control subsystem (102) to the HFCAG subsystem (107) exceeds a precisely-predetermined maximum value for normal operation (which is lower than the maximum value for surges), feedback from the precise detection of current (106) to the control subsystem (102) causes the control subsystem (102) to act to shut-down the said power supply current for a predetermined period of time. This said action prevents over-heating of components within the circuit of the F-IFACG subsystem (107). The overall time for response from the said advent of excess current to the completion of the said shut-down is slower than that required to act to limit the said power supply current. The said fast-limiting action on the said power supply current facilitated by the fast acting detection of current (103) permits the control process to effect a safe shut-down of the power supply current in the event of a surge in the said power supply current, as may occur in the event of a short-circuit at the induction loop (coil) (108).
Voltage spike detection (105) monitors the high voltages produced within the HFACG subsystem (107) within the induction heater system (Fig 1). If a voltage is detected that exceeds the apparent normal operating maximum voltage by a predetermined margin then feedback from the voltage spike detection (105) to the control subsystem (102) causes the control subsystem (102) to perform concurrently two actions: Action A and Action B. Action A is rapidly to sink a large current from within the HFACG subsystem (107) to dissipate energy to prevent the growth of the said voltage spike and thereby safely limit the magnitude of the said voltage spike. Action B is to effect a shut-down for a predetermined period of time of the power supply current to the HFACG subsystem (107). These two said actions (A and B) permit the control process to effect a safe shut-down of the power supply current in the event of a voltage spike within the HFACG subsystem (107), as may be occasioned by a short-circuit or circuit interruption at the induction loop (coil) (108).
Detection of abnormal frequency (106) monitors the oscillation frequency of the HFACG subsystem (107) within the induction heater system (Fig 1). If the said oscillation frequency is outside of the predetermined operational oscillation frequency range of the induction heater system (Fig 1), feedback from the detection of abnormal frequency (106) to the control subsystem (102) causes the control subsystem (102) to act to shut-down the said power supply current for a predetermined period of time. This said action prevents over-stressing of components within the circuit of the HFACG subsystem (107).
The control subsystem (102) within the induction heater (Fig 1) can effect a shut-down of the HFACG subsystem (107) within the induction heater system (Fig 1) for a predetermined time in dependence on the said feedback from the various monitoring (detection) subsystems (103, 104, 105 and 106) that may be arranged to reduce the duty cycle of the induction heater to: avoid immediate further recurrence of the effects of the fault condition on the operation of the HFACG subsystem (107); mitigate stress upon the circuit of H FACG subsystem (107) and the other circuits of the induction heater system (Fig 1); and through the consequent effect on the behaviour of the said induction heater system to indicate to the user of the said induction heater system that a fault condition is in existence in respect of the said induction heater system, so that appropriate corrective actions or other actions may be taken by the user.
The control subsystem (102) within the induction heater (Fig 1) also operate an indicator device or devices in dependence on the said feedback from the various monitoring (detection) subsystems (103, 104, 105 and 106) to indicate to the user of the said induction heater system that a fault condition is in existence in respect of the said induction heater system, so that appropriate corrective actions or other actions may be taken by the user

Claims (4)

  1. Claims The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 1. A closed-loop circuit-protection control process for an induction heater wherein a control subsystem either or both inhibits and alters current and voltage to and from variously the input of, the output of and intermediate points within the High Frequency Alternating Current Generator ("HFACG") subsystem of the said induction heater, in response to closed-loop feedback, at speeds in dependence on the said feedback, the said feedback being separately or in combination, from:- (1) means to detect, according to predetermined criteria, voltage spikes in the said HFACG subsystem of the said induction heater, and send a feedback signal or feedback signals to the said control subsystem for rapid response; (2) means to detect predetermined specified characteristics in the frequency of oscillation in the said HFACG subsystem of the said induction heater, and send a feedback signal or feedback signals to the said control subsystem; (3) means to detect, according to predetermined criteria, rapid surges in the power supply current drawn by the said HFACG subsystem of the said induction heater, and send a feedback signal or feedback signals to the said control subsystem for rapid response; (4) means to detect accurately, according to precise predetermined criteria, excess power supply current drawn by the said HFACG subsystem of the said induction heater, and send a feedback signal or feedback signals to the said control subsystem.
  2. 2. A closed-loop circuit-protection control process for an induction heater as claimed in claim 1, wherein the response of the control subsystem to some or any of the feedback described in claim 1 involves a shut-down of the HFACG subsystem for a predetermined time in dependence on the said feedback that may be arranged to reduce the duty cycle of the said induction heater.
  3. 3. A closed-loop circuit-protection control process for an induction heater as claimed in any of the claims 1 or 2, wherein the response of the control subsystem to some or any of the feedback described in claim 1 involves producing such an effect on the behaviour of the said induction heater as to indicate to the user of the said induction heater that a fault condition is in existence with respect to the said induction heater.
  4. 4. A closed-loop circuit-protection control process for an induction heater as claimed in any of the claims 1, 2 or 3, wherein the response of the control subsystem to the some or any of the feedback described in claim 1 includes operation of an indicator device or devices in dependence on the said feedback so as to indicate to the user of the said induction heater that variously some fault condition is, or some fault conditions are, in existence with respect to the said induction heater
GB1317083.2A 2013-09-26 2013-09-26 Induction heater circuit protection closed loop control process Withdrawn GB2518634A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1317083.2A GB2518634A (en) 2013-09-26 2013-09-26 Induction heater circuit protection closed loop control process

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1317083.2A GB2518634A (en) 2013-09-26 2013-09-26 Induction heater circuit protection closed loop control process

Publications (2)

Publication Number Publication Date
GB201317083D0 GB201317083D0 (en) 2013-11-06
GB2518634A true GB2518634A (en) 2015-04-01

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB1317083.2A Withdrawn GB2518634A (en) 2013-09-26 2013-09-26 Induction heater circuit protection closed loop control process

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1370865A (en) * 1972-04-10 1974-10-16 Matsushita Electric Ind Co Ltd Induction heating equipment
US4010342A (en) * 1974-10-29 1977-03-01 Roper Corporation Induction cooking appliance having improved protection circuits
JPS544334A (en) * 1977-06-10 1979-01-13 Tokyo Shibaura Electric Co Method of making nickel active material for alkali cell
JPS54147543A (en) * 1978-05-10 1979-11-17 Matsushita Electric Ind Co Ltd Induction heater
JP2006040833A (en) * 2004-07-30 2006-02-09 Mitsubishi Electric Corp Induction heating device
US20080051915A1 (en) * 2006-08-25 2008-02-28 Ameritherm, Inc. Power System Component Protection System for Use With an Induction Heating System
WO2010066096A1 (en) * 2008-12-12 2010-06-17 深圳市鑫汇科科技有限公司 Voltage and current surge protective method and its circuit for induction cooker
FR2958491A1 (en) * 2010-03-31 2011-10-07 Fagorbrandt Sas Inverter feeding device protecting method for induction cooking apparatus, involves forcing control signal to value to set switch in ON state when voltage value greater than maximum threshold value is detected between terminals of switch

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1370865A (en) * 1972-04-10 1974-10-16 Matsushita Electric Ind Co Ltd Induction heating equipment
US4010342A (en) * 1974-10-29 1977-03-01 Roper Corporation Induction cooking appliance having improved protection circuits
JPS544334A (en) * 1977-06-10 1979-01-13 Tokyo Shibaura Electric Co Method of making nickel active material for alkali cell
JPS54147543A (en) * 1978-05-10 1979-11-17 Matsushita Electric Ind Co Ltd Induction heater
JP2006040833A (en) * 2004-07-30 2006-02-09 Mitsubishi Electric Corp Induction heating device
US20080051915A1 (en) * 2006-08-25 2008-02-28 Ameritherm, Inc. Power System Component Protection System for Use With an Induction Heating System
WO2010066096A1 (en) * 2008-12-12 2010-06-17 深圳市鑫汇科科技有限公司 Voltage and current surge protective method and its circuit for induction cooker
FR2958491A1 (en) * 2010-03-31 2011-10-07 Fagorbrandt Sas Inverter feeding device protecting method for induction cooking apparatus, involves forcing control signal to value to set switch in ON state when voltage value greater than maximum threshold value is detected between terminals of switch

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