Method, control circuit for a laundry dryer heated by induction and laundry dryer
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Solution Overview
Problem
Existing tumble dryers with electrical resistance heating face issues of complex and costly maintenance due to moving electrical connections, high power consumption, and inefficient drying, while heat pump tumble dryers have longer drying times and limited temperature range, necessitating an alternative control method for precise temperature regulation.
Innovation Solution
An induction heating system that measures the resonant frequency of an oscillating circuit to determine the drum temperature without external sensors, using a microcontroller to filter fluctuations and adjust heating power based on temperature thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If electrical resistance heating elements are used to heat the drum, then heating efficiency is improved, but power consumption increases and maintenance complexity increases due to moving electrical connections
Solution Approach 1:
The patent replaces electrical resistance heating with induction heating. Instead of using electrical resistance elements that require moving electrical connections (brushes, slip rings), the invention uses an induction coil to generate a magnetic field that induces eddy currents in the drum, which then self-heats. This substitutes the mechanical electrical connection system with a contactless electromagnetic field-based heating system, eliminating wear and maintenance issues while maintaining high heating efficiency.
Solution Approach 2:
The patent changes the heating mechanism from resistive heating to induction heating by altering the physical parameters of the heating system. The induction coil operates at specific frequencies to generate magnetic fields that penetrate the drum, inducing currents that produce heat internally within the drum material. This parameter change enables contactless heating with improved efficiency and reduced power consumption.
2Loss of energy
If electrical resistance heating elements are used, then direct heating is achieved, but maintenance costs increase due to wear of brush contacts
Solution Approach 1:
The patent eliminates the mechanical electrical connection system (brushes, slip rings, commutators) by using induction heating. The induction coil generates a magnetic field that couples with the conductive drum, inducing eddy currents that produce heat without any physical contact. This substitution removes the wearing components entirely, eliminating maintenance requirements for electrical contacts while preserving direct and efficient heat transfer to the drum.
3Use of energy by moving object
If heat pump circuit is used, then energy efficiency is improved, but drying time increases due to lower temperature range
Solution Approach 1:
The patent merges the heat pump system with an induction heating system in a hybrid configuration. The heat pump provides efficient heating during normal operation, while the induction heating system can be activated to rapidly increase temperature when faster drying is required. This combination allows the system to maintain high energy efficiency while gaining the ability to operate at higher temperatures to reduce drying time when necessary.
Solution Approach 2:
The patent implements a dynamic control system that can switch between heat pump heating and induction heating modes based on drying requirements. The control circuit monitors drying progress and environmental conditions, dynamically selecting the appropriate heating mode or combining both modes to optimize the balance between energy efficiency and drying speed.
4Measurement precision
If external temperature sensors are used for drum temperature measurement, then temperature control precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces physical temperature sensors (thermocouples, RTDs, infrared sensors) with a contactless electromagnetic measurement method. By monitoring the resonant frequency and impedance changes of the induction coil, the system infers drum temperature without any physical contact or additional sensing components. This substitution eliminates the need for external temperature sensors, reducing device complexity and cost while maintaining adequate temperature measurement precision for control purposes.
Solution Approach 2:
The patent uses the induction coil itself as an intermediary for temperature measurement. The coil's electrical characteristics (resonant frequency, impedance) serve as a mediator that indirectly indicates drum temperature through the temperature-dependent changes in magnetic permeability and electrical resistance of the drum material. This intermediary approach enables temperature monitoring without direct sensor contact.
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 method enables efficient, gentle, and accelerated drying with reduced maintenance costs and improved temperature control, eliminating the need for external sensors and enhancing the energy efficiency of heat pump tumble dryers.
Implementation Method 1
an induction coil connected to an oscillating circuit, and a method for determining the temperature of a heater
Implementation Method 2
driving an induction heater to heat the drum of a clothes dryer
Implementation Method 3
an induction coil connected to an oscillating circuit
Data Source
Figure 1~2
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AI summary
The present invention relates to a method for controlling an induction heater of a tumble dryer, comprising controlling an induction heater to heat the drum of a tumble dryer, interrupting the activation of the induction heater for a time interval so that the resonant circuit of the induction heater can oscillate freely, measuring the resonant frequency of the resonant circuit during the time interval, and determining the temperature of the drum based on the measured resonant frequency.