Synchronous Motor Starting via Shared Frequency Converter
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Solution Overview
Problem
Household appliances with permanent magnet synchronous engines face limitations in speed variability and loading due to the fixed frequency of the AC voltage network, leading to inefficient operation and increased costs when using multiple frequency converters.
Innovation Solution
A household appliance design that includes at least one electrical synchronous engine, a frequency converter, a switching device, and a control unit, allowing the engine to operate on either the AC voltage network or the frequency converter, with the frequency converter being operated at a frequency less than the fixed frequency of the AC voltage network, enabling efficient starting and switching between the two power sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a frequency converter is used for controlled operation of synchronous motors, then speed control and load sensing are improved, but device complexity and costs increase
Solution Approach 1:
The patent merges multiple frequency converter functions into a single shared converter that can sequentially control multiple synchronous motors. The converter is time-multiplexed across different motors, allowing one converter to perform the work of multiple converters while reducing overall system complexity and cost.
Solution Approach 2:
The frequency converter is designed as a universal device that can serve multiple different synchronous motors in a household appliance. It can be configured to work with different motor types (drain pump motor, circulation pump motor, fan motor) through software control, making it a multi-functional component that replaces what would traditionally require separate dedicated converters for each motor.
2Adaptability or versatility
If multiple frequency converters are used for controlled operation of multiple synchronous motors, then speed control and load sensing are improved, but costs increase
Solution Approach 1:
The patent combines multiple frequency converter units into a single shared converter that serves multiple motors. By time-multiplexing the converter across different motors (e.g., draining phase, washing phase, drying phase), the system achieves the functionality of multiple converters while using only one physical device, thereby reducing costs.
Solution Approach 2:
The system dynamically assigns the frequency converter to different motors based on operational requirements. The converter is activated for specific motors during specific operational phases (e.g., drain pump during draining, circulation pump during washing, fan during drying), allowing flexible resource allocation and eliminating the need for permanent dedicated converters for each motor.
3Loss of energy
If synchronous motors operate directly on AC mains, then efficiency is improved (no converter losses), but starting behavior and speed variability are worsened
Solution Approach 1:
The frequency converter performs preliminary action by providing controlled start-up sequences for the synchronous motors before they are switched to direct AC mains operation. The converter gradually increases frequency and voltage to appropriate levels, preventing sudden inrush currents and mechanical shocks, then transfers control to the mains once the motor is running smoothly.
Solution Approach 2:
The system uses periodic action by applying frequency converter control only during specific operational phases (starting, transient conditions) and then switching to continuous AC mains operation for steady-state running. This periodic application of converter control minimizes energy losses while providing assistance exactly when needed for starting and transient performance.
4Ease of manufacture
If synchronous motors are designed for fixed mains frequency operation, then manufacturing simplicity is improved, but speed variability and load sensing are worsened
Solution Approach 1:
The frequency converter acts as an intermediary between the fixed-frequency AC mains and the synchronous motors. It converts the fixed-frequency mains power into variable-frequency output that can control motor speed, thereby enabling speed variability and load sensing without requiring complex motor designs. The converter handles all the complexity of variable frequency control while the motors remain simple fixed-frequency designs.
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 reliable starting and efficient operation of synchronous engines, reducing converter losses to only during startup, while also enabling flexible speed control and loading options, thereby improving efficiency and reducing costs compared to traditional multiple frequency converter setups.
Implementation Method 1
a frequency converter; a switching device configured to selectively connect the at least one synchronous motor either to the frequency converter or to the AC voltage network
Data Source
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AI summary
The invention relates to a household appliance for operation on a fixed-frequency AC power grid (N, L), comprising at least one electric synchronous motor (M1, M2, M3, Mx), a frequency converter (1), a switching device (2) configured to selectively connect the at least one synchronous motor (M1, M2, M3, Mx) either to the frequency converter (1) or to the AC power grid (N, L), and a control unit (3) configured to connect the at least one synchronous motor (M1, M2, M3, Mx) to the frequency converter (1) by means of the switching device (2) in order to start the synchronous motor (M1, M2, M3, Mx), wherein the frequency converter (1) is operated at a frequency lower than the fixed frequency of the AC power grid (N, L), and, after the synchronous motor (M1, M2, M3, Mx) has started, to increase the frequency of the frequency converter (1), and the at least one Synchronous motor (M1, M2, M3,Mx) to be disconnected from the frequency converter (1) by means of the switching device (3) and connected to the AC mains supply (N, L).