Abstract: A load matching circuit is disclosed for use with a frequency controlled power supply. The load matching circuit includes an input connectable to the frequency controlled power supply and an output connectable to the load, such as an induction heating coil. A load matching section is connected between the input and the output to provide enough resonance to allow the power supply to operate at or below the maximum frequency when the load is connected to the power supply and at or above the minimum frequency when the load is disconnected from the power supply. In this manner, a solid-state variable frequency power supply can continue to run even when the external load is disconnected from the power supply.

Abstract: There is disclosed a heating apparatus of a magnetic induction heating system. This heating apparatus comprises a control mode for a power source (excitation circuit) for supplying power to magnetic field generating means (exciting coil). The control mode includes a first mode for controlling an ON width by fixing the number of ON times per unit time of a switching element of an inverter circuit of a voltage resonance system when power larger than a predetermined value is supplied, and a second mode for controlling the number of ON times per unit time by fixing the ON width of the switching element to a predetermined ON width.

Abstract: A coil/capacitor combination useable as an induction furnace includes a reactive capacitor bank directly bolted to the coil and protected from coil fields by shields and heat sink plates. The coil includes a selectively openable switch for placing the coil assembly on and off of a moving strip. The switch is operated by deflecting coil turns within the natural resiliency of the turns themselves.

Abstract: Induction heating apparatus has a series inductor between an AC source and a parallel tank circuit.

Abstract: A fixing device for an image forming apparatus includes an inverter circuit for induction heating. In the inverter circuit, a main switch Q1 drives one end of a work coil L1 whose other end is connected to a power source. A serial connection of a capacitor Cs and a subswitch Q2 is connected to opposite ends of the coil L1 in parallel such that one end of the capacitor Cs is connected to the power source E. A second capacitor C1 is connected to the subswitch Q2 in parallel. For a capacitance of 0.1 &mgr;F of the capacitor C1, the factor of the coil L1 and that of the capacitor Cs are selected to be between 70 &mgr;H and 100 &mgr;H and between 1.8 &mgr;F and 5 &mgr;F, respectively. The inverter circuit is operable with optimal efficiency in the event of PWM (Pulse Width Modulation) control using a fixed frequency.

Abstract: Induction heating apparatus has a series inductor between an AC source and a parallel tank circuit.

Abstract: An apparatus and method is provided for conductively bonding at least two conductors together. An inductive coil generates a magnetic field when electrical current is run therethrough. A magnetic concentrator is disposed near the inductive coil and adjacent which the two conductors can be positioned for concentrating the magnetic field on the conductors. The concentrator is independent of the conductors. Pressure is applied to the conductors. The concentrator concentrates the magnetic field generated by the inductive coil on the conductors, thereby heating the conductors under pressure and electrically bonding the conductors together.

Abstract: A method for simultaneously hardening a group of cams on a camshaft comprises first heating the group of cams at low power for at least one heating interval, then pausing the heating for a pause interval during which no power is applied to the group of cams, and then subsequently heating the group of cams at high power for one heating interval. The pause intervals, during which no power is applied to the group of cams, are sufficient as to allow heat stored in the cams to distribute uniformly throughout the cams. Each group of cams is hardened by a linear inductor and the regions of the camshafts that are not to be hardened are shielded by a cooling device.

Abstract: An alloying system for a galvanized steel sheet, the alloying system using an induction heating coil, wherein an impedance matching apparatus is provided between the induction heating coil and a high frequency power source. The impedance matching apparatus comprises a matching transformer having a plurality of intermediate contact points for arbitrarily selecting a turn ratio, and a switching device for alternative changeover of the intermediate contact point, whereby even when the load impedance of the steel sheet varies, maximum power source output is obtained, such that an appropriate heating temperature necessary for forming an alloy layer of the steel sheet can be supplied.

Abstract: A new apparatus and process for soldering surface-mount and through-hole type electronic components into a printed circuit board (PCB) in an automated fashion utilizing localized electromagnetic induction heating. Current manufacture technology for packaging electronic components depends exclusively on the reflow and wave soldering processes. Both processes heat up to relatively high temperature the entire assembly, namely its PCB and all the electronic components been soldered into it. Such high temperature environment frequently causes components damage resulting in rejects and/or demanding rework. With this invention however, during a soldering operation only the leads and pads, or joints, being soldered are heated but neither the body, or casing, of said electronic components nor the dielectric material forming said PCB are heated. Because of this selectively localized heating, the invention permits to reduce cost and improve the quality and reliability of manufactured products.

Abstract: An induction furnace having a voltage source series inverter, a load circuit having a combination of an induction coil and a resonating capacitor bank, and control circuitry to phase lock the inverter frequency to the natural resonant frequency of the load. The capacitor bank can be divided into two groups, one across the output of the inverter and the other in series with the load. This arrangement allows for the division of the inverter voltage across the furnace coil according to the ratio of the two capacitances. The inverter uses pulse width modulation and is buffered from the load circuit by means of a small series connected inductor. Additionally, the system can have a common power supply system that supplies power in any desired proportion to a plurality of induction furnaces.

Abstract: A cap sealing unit for securing foil-polymer laminate innerseals to containers has an air cooled electronics cabinet that may be sealed in accordance with NEMA 4 standards. Heat sinks in the bottom of the electronics cabinet and the top of the sealing head are cooled by two external, wash-down safe fans disposed between the cabinet and the sealing head. The fans draw air in opposite directions, one toward the cabinet and the other toward the sealing head. The cap sealer can be operated with interchangeable flat or tunnel sealing heads of various sizes and coil windings that can be connected to the power supply with plug-in shielded connector assemblies.

Abstract: A system for melting metal and holding molten metal, comprises a rectifier unit receiving AC electric power and outputting DC electric power, a plurality of inverter units, each receiving the DC electric power output by the rectifier unit and outputting AC electric power; and a plurality of induction furnaces each receiving the electric power output by a respective inverter unit. Each inverter unit comprises a plurality of inverter modules connected in parallel, each module independently being connectable to and disconnectable from the rectifier unit and the furnace. The rectifier unit comprises a plurality of rectifier modules connected in parallel, each module independently being connectable to and disconnectable from the AC supply and the inverter units.

Abstract: An induction heating device for controlling the temperature distribution in an electrically conductive material, or susceptor, when heated by induced eddy currents in the material. A non-electrically conductive material can be heated in a controlled manner by placing the material near to the susceptor. Variable power is applied to multiple induction coil sections wound around the length of the susceptor from a power source by one or more switching circuits. The coil sections can be overlapped or counter-wound between adjacent coil sections, or provided power in a cascaded manner, to achieve desired temperature distributions in the susceptor. A control circuit is used to control the power applied to each coil section and the output of the power source. By placing a non-electrically conductive material near to the susceptor the material can be heated in a controlled manner.

Abstract: For use in the heating of foodstuffs by induction, use is made of an energy converter between energy taken from the mains supply via a rectifier and a high frequency oscillation. Such a converter is frequently based on the maintenance of an oscillation in a parallel resonant circuit (CR, LR) which may be disposed in a converter bridge (S1, S2, S3, S4) of controlled switches. It has turned out to enhance the efficiency considerably to let the parallel resonant circuit be series connected to a self-inductance L1 which connects it to the DC source UDC. A series resonant circuit is thereby created which is active during supply of energy and which in a simple fashion reduces the load on the participating switches.

Abstract: A high-frequency inverter having a simple circuit construction capable of executing a constant-frequency operation and a zero-volt switching operation and an induction heating cooker using the high-frequency inverter are disclosed. The high-frequency inverter is comprised of an inverter circuit for converting a direct current from a DC power source into a high-frequency current and a control circuit for controlling the inverter circuit. The inverter circuit is comprised of: a one-transistor inverter constructed of a heating coil whose one terminal is connected to one terminal of a DC power source, a first switching element connected in series between the other terminal of the heating coil and the other terminal of the DC power source, and a first resonance capacitor connected so as to form a resonance circuit with the heating coil; and a series circuit connected in parallel with the heating coil and constructed of a second switching element and a second resonance capacitor.

Abstract: This invention pertains to an electromagnetic induction fluid heating apparatus equipped with a heating element constructed from a conductive material installed in a fluid flow passage, a coil installed around this heating element, and a high frequency electrical current generator for this coil. In particular, this heating element is a layered component that allows electrical conduction between metallic plates. This heating element is formed so that electrical current vortices occur throughout this layered component. By forming a fluid flow passage that allows mixing within this layered component, the electrical power efficiency becomes 100%. Moreover, this high frequency electrical current generator is an invertor that uses semiconductor power devices such as SIT, B-SIT, MOSFET, IGRT, and MCT, etc. When the preferred PWM system (Pulse Width Modulation) is used, the heating efficiency (affected by the efficiency of the invertor, etc. matched with this layered component) exceeds 90%.

Abstract: Circuits for high frequency energy supply for cooking pots, etc. utilize resonant circuits in which the coil for the energy transfer forms a part. Furthermore circuits of the inverter type are used. It has turned out to be advantageous to use an extra circuit which gives the current feed from the rectifier of the power supply unit to the inverter a period of oscillation which is less than or equal to the period of oscillation of the resonant circuit. In this manner an efficient control of the supplied power is obtained, and the losses are reduced. Furthermore measuring signals may be derived which may be used for increasing the safety with respect to incorrect use.

Abstract: A method and apparatus for fusion joining polyethylene pipe. A power source supplies an input power to an input of a power supply. The input power has generally constant current and is converted to an output power at a relatively high frequency. The relatively high frequency output power is delivered to an installation tool. The output power delivered to the installation tool is controlled. The output power can be controlled as a function of ambient temperature surrounding the installation tool.

Abstract: High frequency electrical heating apparatus in which metal parts are heated as they are advanced,either for annealing or forge welding purposes,and in which the electrical heating current is supplied by solid state D.C. to A.C. inverter through a load matching and frequency control circuit which maintains the desired load current and current frequency with changes in the load impedance caused by the metal parts as they are advanced.

Abstract: An induction heating generator is disclosed. The generator controls the power delivered to a work coil via a plurality of resistor/bias control switches coupled in parallel and a controller, thereby eliminating the expensive and difficult to troubleshoot SCR control circuits associated with prior art generators. By sequentially switching the bias control switches, the controller can progressively lower the input voltage to a controlled switch to thereby alter its conducting state to provide stepped power increases to the work coil. The work coil is de-energized by opening the bias control switches in reverse sequential order.

Abstract: A ripple current generator for an induction heating apparatus includes a resonant circuit with a current injecting self-inducting coil (6), a capacitor (13), an induction heating coil (14) and a high-frequency controlled power switch (12). The current injecting self-inducting coil (6) is saturable and mounted in series with a parallel assembly consisting of two arms; a first arm (B.sub.1) containing the switch (12) and a second arm (B.sub.2) containing a capacitor (13) mounted in series with the induction heating coil (14). The self-inducting coil includes a magnetic circuit that automatically reaches saturation during the resonance phase of the oscillating circuit. The generator is useful in household cooking appliances such as induction plates, cookers or deep fryers, as well as industrial induction heating equipment for treating metal components.

Abstract: A delay timer incorporated into an induction cooking cartridge permits the use of the induction cooking cartridge with conventional modular cooktops including bi-metal power switches without damage to the induction circuitry.

Abstract: A device for inductive cross-field heating of flat metallic goods has at least one pair of inductors having each one iron core provided with a groove for receiving a lead that extends in the transport direction. The grooves and leads of both inductors of a pair of inductors are mirror symmetrical and the leads of each inductor form two independently switchable lead systems. Each lead system has sections that extend substantially in the transport direction of the metallic goods and whose center lines extend symmetrically to a central axis of the inductor parallel to the transport direction. The individual poles of the lead systems consist of maximum two leads. Each pole of a lead system is arranged between the poles of the other lead system. A uniform temperature distribution in the goods to be heated is achieved by synchronizing the offsetting in time the moments when both lead systems are switched.

Abstract: An appliance control circuit comprising dual processor control for enhanced control operation and agency safety redundancy. A first processor is disposed in operative communication with operator control switches for primarily controlling the supply of power for principal appliance functions. A second processor is in operative communication with the first processor and disposed for primarily monitoring appliance safety detection circuits and for controlling agency circuitry redundancy through a second switch in series with the first switch. The first and second switches comprise agency circuitry for enabling said supply of power when said first switch is directly enabled by the first processor and the second switch is directly enabled by the second processor for safety redundancy of said power supply.

Abstract: A high-frequency power supply which is primarily intended for use with an inductive heating apparatus. The high-frequency power supply has a pre-regulator for emitting a constant output voltage, an inverter for generating a constant output voltage, and an output network for amplifying the constant output voltage and converting the constant output voltage to a high-frequency constant output current. The power supply disclosed generates a very high frequency ac output, drives a wide range of possible loads, minimizes root mean square input current for a given output power, and can be powered from a wide range of input power sources.

Abstract: A multi-furnace control system selectively delivers preselected percentages of available power to furnaces of the system, preferably designated as either a melt furnace or a hold furnace. The power supply delivers power to both furnaces. A capacitor station in parallel connection to the power supply and the furnaces is tuned to form a tank circuit therewith. Switches control the selected power delivered to the furnaces respectively and control the delivery of a first portion of the power for holding molten product in the hold furnace as the master control. A remaining portion of the power is then delivered for melting product in the melt furnace. The capacitor station acts as a reactive tank for both furnaces.

Abstract: An induction cooking apparatus and method for inductively heating cookware is provided. An analog/digital circuit, including a microprocessor, generates a plurality of gating pulses for operating the power inverter circuit and monitors the operation of the power inverter circuit. The microprocessor provides signals to start and stop the inverter circuit, and determines a period of uninterrupted power inverter circuit operation corresponding to a desired cooking temperature. Analog circuitry is provided for sustaining operation of the power inverter circuit after the power inverter circuit is started, and for compensating for variations in cookware materials.

Abstract: In a switching device of an induction heating cooker, an oppositely poled diode for conducting a reverse current is coupled across the collector-emitter portion of a switching element provided in the first switching device, and turn-ON operation of the switching devices does not OCCUR in normal operation of the DUTY FACTOR T.sub.2 /T.sub.1 .apprxeq.0.5.

Abstract: An inductive hot point heating system is regulated or controlled by an oscillation packet control, which uses a symmetrical pattern of complete mains half-waves. The switching takes place in the zero passage and is symmetrical in such a way that there is no d.c. voltage component in the mains. It also contains an optical temperature monitoring of the plate covering the cooking point with an infrared photosensor, which determines the temperature on the basis of its predetermined spectral range.

Abstract: A power transistor driving circuit for use in an electromagnetic induction heating device comprises an induction coil circuit and a driving circuit. The induction coil circuit is provided with an induction connected with an oscillating circuit made up of capacitances and resistances. The oscillating circuit is provided with at least one power transistor for producing a high frequency switching. The driving circuit comprises at least one quick switching circuit provided with two transistors between which a resistance and an inductance are connected therewith in series. One end of the inductance is connected with the gate of the power transistor for accelerating the reverse current flow of the gate so as to shorten the switching time of the power transistor and to reduce the switching power loss of the power transistor at the time when the power transistor is turned off.

Abstract: A dual push-pull heating device of induction cooker having multiple burners is provided with a microprocessor controlling a logic amplifying drive circuit outputting a high-frequency pulse signal, so as to drive alternately at least a power element or power transistor having two parallel electromagnetic induction coils arranged at an end thereof in such a manner that a common end of said induction coils is connected with a common connection point of a relay whose normal close point is connected with a non-common end of one of the induction coils and whose normal open point is connected with a non-common end of another one of the induction coils.

Abstract: An induction heater comprises a coupled pair of inverters and an induction head for generating heat, coupled to the second inverter. The first inverter operates at a constant frequency, but the total output current is controlled through pulse width modulation. The output current is rectified and provided as a DC input voltage, proportional to the total output current of the first inverter, to the second inverter. The second inverter operates at an adjustable frequency which is selected by the user to optimize heating. The power delivered to the induction heater is dependent on the output voltage of the second inverter, which is dependent on the input voltage to the second inverter, and the output current of the first inverter.

Abstract: A dual push-pull induction heating drive circuit comprises an oscillation triggering control circuit regulating the ON-OFF switch of the circuit activation, a switching logic circuit bringing about two exclusive pulse signals serving to drive via an amplifying circuit a dual push-pull switching output circuit having two power elements connected to an induction coil, a pulse width modulating circuit having a controlled comparing element capable of sending out adjustable pulse, and a synchronous detection comparing circuit having at least a comparing element and having an input end in communication with an induction coil and another input end connected with a power source and further having an output end connecting with the switching logic circuit and sending out synchronous pulse signals to a differentiation circuit to bring about synchronous differentiation pulse signals, which are received by the pulse width modulating circuit so as to generate the power control pulse signals serving via the switching logic