Induction heater having a power inverter and a variable frequency output inverter
First Claim
1. An induction heater comprising:
- a first inverter having a first inverter output;
a variable frequency output inverter having a variable frequency inverter input;
a first coupling circuit in electrical communication between said first inverter output and said variable frequency output inverter input, wherein said variable frequency output inverter is cascaded with said inverter;
an induction head; and
a second coupling circuit in electrical communication between said variable frequency output inverter and said induction head.
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Accused Products
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.
107 Citations
32 Claims
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1. An induction heater comprising:
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a first inverter having a first inverter output; a variable frequency output inverter having a variable frequency inverter input; a first coupling circuit in electrical communication between said first inverter output and said variable frequency output inverter input, wherein said variable frequency output inverter is cascaded with said inverter; an induction head; and a second coupling circuit in electrical communication between said variable frequency output inverter and said induction head. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An induction heater comprising:
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a phase modulated inverter operable at a first frequency; first coupling means, having an AC input receiving a first output signal from said phase modulated inverter, for providing a DC output signal having a magnitude responsive to the phase modulation of said phase modulated inverter; an adjustable frequency inverter receiving said DC output signal, wherein said adjustable frequency inverter provides a second output signal having a magnitude responsive to the magnitude of said DC output signal; an induction head for coupling energy to a workpiece in response to an applied electrical signal; second coupling means in electrical communication between said adjustable frequency inverter and said induction head; and control means, in electrical communication with said phase modulated inverter, for providing a feedback signal indicative of the power output of said induction head and for controlling the phase modulation of said phase modulated inverter in response to said feedback signal. - View Dependent Claims (18, 19)
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20. An induction heater comprising:
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first inverter means for receiving a first DC signal and providing a first modulated AC signal; second inverter means for receiving a second DC signal and providing a second AC signal at an adjustable frequency, said second AC signal having a magnitude responsive to the magnitude of said second DC signal; first coupling means, in electrical communication between said first inverter means and said second inverter means, for receiving said first AC signal and converting said first AC signal to said second DC signal, said second DC signal having a magnitude responsive to the modulation of said first AC signal; an induction head for coupling energy; and second coupling means, in electrical communication between said second inverter means and said induction head, for receiving said second AC signal and providing a third AC signal to said induction head, said third AC signal having a magnitude responsive to a magnitude of said second AC signal. - View Dependent Claims (21, 22, 23, 24, 25)
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26. A method of induction heating comprising the steps of:
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inverting a first DC signal to provide a first AC signal having an adjustable pulse width; transforming the first AC signal into a second DC signal having a magnitude responsive to the pulse width of the first AC signal; inverting the second DC signal at a selectable frequency to provide a second AC signal having a magnitude responsive to the magnitude of the second DC signal; providing a third AC signal, having a magnitude and frequency responsive to the magnitude and frequency of the second AC signal, to an induction head for coupling energy. - View Dependent Claims (27, 28, 29, 30)
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31. An induction heater comprising:
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first inverter means for receiving a first DC signal and providing a first modulated AC signal; second inverter means for receiving a second DC signal and providing a second AC signal at an adjustable frequency, said second AC signal having a magnitude responsive to the magnitude of said second DC signal; first coupling means, in electrical communication between said first inverter means and said second inverter means, for receiving said first AC signal and converting said first AC signal to said second DC signal, said second DC signal having a magnitude responsive to the modulation of said first AC signal; and an induction head coupled to the second inverter means. - View Dependent Claims (32)
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Specification