Dryer Drum Motor Speed Control Across Selectable Drying Ranges
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Solution Overview
Problem
Existing tumble dryers using single-phase asynchronous motors have limited speed variability, resulting in inefficiencies and reduced performance, while multi-motor concepts operate at constant speeds, lacking flexibility in drying programs.
Innovation Solution
A domestic appliance with a power electronics unit that controls an electric machine to vary speed across predefined ranges, using a current detection unit to optimize motor current and power delivery for improved drying performance and user-selectable programs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-phase asynchronous motor is used to drive the drum, then the device complexity is reduced, but the speed variability is limited and performance is reduced
Solution Approach 1:
The patent applies dynamics by enabling the electric machine to operate at multiple variable speeds through power electronics control, allowing the drum rotation speed to be dynamically adjusted according to different drying programs. This resolves the contradiction by making a single motor adaptable to multiple speed requirements without increasing device complexity through multiple motors.
Solution Approach 2:
The patent changes the operational parameters of the electric machine by controlling it to operate in different speed ranges (first, second, and third speed ranges) based on drying program requirements. This allows a single motor to achieve the versatility of multiple motors through parameter variation, resolving the contradiction between device complexity and speed variability.
2Productivity
If the electric machine operates at high speed, then drying efficiency is improved, but mechanical stress on laundry increases
Solution Approach 1:
The patent uses dynamic speed adjustment to switch between different operating modes: high speed for efficient drying when mechanical stress is acceptable, and low speed for gentle drying when preserving laundry integrity is prioritized. This resolves the contradiction by making the system adaptable to different operational requirements rather than operating at constant high speed.
Solution Approach 2:
The patent implements periodic alternation between different speed ranges during the drying cycle, switching between high-speed efficient drying phases and low-speed gentle drying phases according to the drying program. This periodic action resolves the contradiction by balancing drying efficiency and mechanical stress reduction over time.
3Adaptability or versatility
If multiple motors are used to drive different components, then different speed control is achieved, but device complexity increases
Solution Approach 1:
The patent makes a single electric machine universal by enabling it to drive multiple components (drum and fan wheel) at different speed ranges through power electronics control. This multi-functionality resolves the contradiction by achieving the versatility of multiple motors without the complexity of actually installing multiple motors.
Solution Approach 2:
The patent merges the functions of multiple motors into a single electric machine by using one motor to drive both the drum and fan wheel, with speed control achieved through power electronics rather than mechanical transmission. This combining approach resolves the contradiction by reducing device complexity while maintaining the ability to operate components at different speeds.
4Adaptability or versatility
If a frequency converter is used to control motor speed, then speed variability is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the electrical parameters (frequency and voltage) supplied to the electric machine through a frequency converter, enabling smooth speed variation across multiple ranges. This parameter control approach resolves the contradiction by achieving speed flexibility through electrical parameter adjustment rather than mechanical means, managing device complexity through electronic control.
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 solution allows for flexible speed control of the electric machine, enhancing drying efficiency, reducing mechanical stress on laundry, and offering customizable drying times and noise levels through variable speed ranges, improving overall appliance performance.
Implementation Method 1
the power electronics unit (6) is designed to vary a speed of the electric machine (4) by an actuation effected by the control and/or regulating unit (7)
Implementation Method 2
a electric machine (4), in particular a three-phase asynchronous machine, by which a drum (3) of the household appliance (1) is driven
Implementation Method 3
a current detection unit is provided, which is designed to detect a motor current flowing through the electric machine (4)
Data Source
AI summary
The invention relates to a household appliance (1) for drying laundry, comprising an electric machine (4) designed to drive at least one drum (3) of the household appliance (1), and a power electronics unit (6) electrically coupled to the electric machine (4), which is controllable by a control and/or regulating unit (7) and is designed to vary the speed of the electric machine (4) by means of a control effect effected by the control and/or regulating unit (7), wherein the control and/or regulating unit (7) is designed to effect a change in speed by controlling the power electronics unit (6) depending on predefined speed operating ranges, and wherein at least two drying programs selectable by an operator, each with a characteristic speed operating range, are predefined in which the electric machine (4) is operated at different speeds.The invention also relates to a method for operating such a household appliance (1).