Induction Cooktop Phase Control for Intermodulation Hum Reduction
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Solution Overview
Problem
Cooktops with multiple heating elements face issues of intermodulation hum and flicker due to simultaneous operation at the same frequency, making independent control of heating powers challenging, especially in induction cooktops, and causing disturbances and voltage peaks in household power networks.
Innovation Solution
A cooktop design where the control unit activates heating elements in different phases of the heating period, allowing independent control of heating powers without flicker or hum, by adjusting the duration of these phases and frequencies, and determining inductance and power factor to tailor heating to the cooking utensil, reducing magnetic interaction interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multiple heating elements are operated simultaneously at the same frequency, then the heating power can be controlled independently for each element, but intermodulation hum and flicker problems occur
Solution Approach 1:
The patent applies periodic action by operating heating elements in alternating phases within a heating period. Instead of simultaneous operation, the control unit activates heating elements in different phases (e.g., first element in phase 1, second element in phase 2), creating a periodic switching pattern that eliminates intermodulation hum while maintaining independent power control through phase duration adjustment.
Solution Approach 2:
The heating period is segmented into multiple phases, with each heating element assigned to a specific phase. This segmentation allows independent control of each element's heating power by adjusting the duration of its assigned phase, while preventing simultaneous operation that causes harmful intermodulation effects.
2Ease of operation
If heating elements are switched on and off periodically to achieve specified average heating power, then the average heating power can be controlled, but voltage peaks and flicker occur in the power network
Solution Approach 1:
The patent uses periodic action with multiple phases within a heating period, where heating elements are activated in different phases rather than simultaneously. This distributed periodic switching pattern reduces the amplitude of power consumption fluctuations, minimizing voltage peaks and flicker in the household power network while maintaining precise control of average heating power through phase duration adjustment.
3Object-generated harmful factors
If induction heating elements are operated at different frequencies to avoid hum, then audible hum is reduced, but independent determination of heating powers becomes impossible
Solution Approach 1:
The patent resolves this contradiction by using periodic action with phase-based operation instead of frequency differentiation. Heating elements operate in different phases of a heating period at the same frequency, which eliminates audible hum through temporal separation while maintaining independent heating power control through adjustment of each phase's duration, enabling precise independent determination of heating powers.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise control of heating powers, reduces flicker and hum, and ensures reliable operation, particularly in induction cooktops, by minimizing power consumption fluctuations and avoiding voltage peaks, while allowing flexible operation tailored to the cooking utensil's magnetic properties.
Implementation Method 1
The heating elements combined to form a heating zone are each supplied with a heating current by a power supply unit
Implementation Method 2
particularly when the heating elements are induction heating units or inductors
Data Source
AI summary
A cooktop is provided that includes heating elements which are combined to a heating zone; a power supply to generate a heating current that operates the heating elements; a switch to open and close a power circuit that includes the power supply and one of the heating elements; and a controller that determines a characteristic variable of the heating current, actuates the switch as a function of a selected power level to operate the heating zone, and activates, in a first operating state, two of the heating elements, which are combined to form the heating zone, in different phases of a heating period.