Device and method for controlling linear compressor
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Solution Overview
Problem
Reciprocating compressors face a trade-off between reducing frictional loss for increased efficiency and maintaining maximum freezing capacity, as adjusting the initial piston position affects both compressor efficiency and freezing capacity, making it difficult to manage overload conditions effectively.
Innovation Solution
A control module for linear compressors that generates an asymmetric motor current by applying a current offset to the detected motor current, allowing for electrical adjustment of the piston's initial position, thereby optimizing efficiency and freezing capacity based on load conditions, and includes a virtual capacitor for high-efficiency operation and overload management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the initial piston position is reduced to decrease stroke and reduce frictional loss, then compressor efficiency is improved, but maximum freezing capacity is reduced
Solution Approach 1:
The patent applies dynamics by making the piston initial position adjustable rather than fixed. The controller electrically moves the piston from its initial position by controlling the motor current, allowing the system to adapt between efficiency mode (small initial position) and capacity mode (large initial position) based on operating conditions.
Solution Approach 2:
The patent changes the parameter of piston initial position dynamically. By applying a current offset to the motor current, the controller adjusts the piston's starting position, thereby changing the stroke length and balancing between frictional loss and freezing capacity requirements.
2Productivity
If the initial piston position is increased to increase stroke and maximum freezing capacity, then freezing capacity is improved, but frictional loss increases and efficiency decreases
Solution Approach 1:
The system dynamically adjusts the piston initial position based on load conditions. During high-load operations, the controller increases the initial position to maximize freezing capacity, while during low-load operations, it reduces the initial position to minimize frictional loss and improve efficiency.
Solution Approach 2:
The piston initial position parameter is changed dynamically through current offset control. The controller adjusts this parameter in real-time based on operating conditions, allowing optimization of both freezing capacity and efficiency under different load scenarios.
3Productivity
If voltage is varied to control compression ratio and freezing capacity, then freezing capacity control is achieved, but compressor efficiency is compromised
Solution Approach 1:
The patent introduces asymmetry by applying a DC current offset to the AC motor current. This asymmetric current control creates an unbalanced magnetic field that electrically shifts the piston's initial position, enabling independent control of stroke and compression ratio while maintaining efficiency.
Solution Approach 2:
The patent replaces the traditional mechanical method of stroke control (physical adjustment of piston position) with an electrical control method. By controlling the motor current and applying current offset, the system achieves stroke and compression ratio control without mechanical modifications.
4Loss of energy
If a physical capacitor is used for resonance control, then high-efficiency operation is achieved, but manufacturing cost increases
Solution Approach 1:
The patent replaces the physical capacitor component with an electronic control algorithm implemented in the controller. The virtual capacitor function is achieved through software-based resonance control, eliminating the need for additional physical components while maintaining resonance operation and efficiency.
Solution Approach 2:
The controller is designed to perform multiple functions: motor control, resonance control, and virtual capacitor emulation. By integrating these functions into a single control unit, the system eliminates the need for separate physical capacitor components, reducing manufacturing cost while maintaining performance.
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
The solution enhances the linear compressor's efficiency and freezing capacity by optimizing the piston's position and using a virtual capacitor for resonance control, effectively managing overload conditions and reducing fabricating costs.
Implementation Method 1
a piston is directly connected to a mover of a linear motor so as to perform a reciprocating motion in response to a linear motion of the motor
Implementation Method 2
When the reciprocating compressor is used for a refrigerator or an air conditioner
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
The control module includes a drive circuitry that drives the linear compressor based on a control signal, a detector that detects a motor current and a motor voltage corresponding to a motor of the linear compressor, an asymmetric current generator that generates an asymmetric motor current by applying a current offset to the detected motor current, and a controller that generates the control signal based on the asymmetric motor current and the detected motor voltage. Such a control module may increase a maximum freezing capacity by appropriately (or optimally) designing (setting) an initial value of a piston in a driving area or an operation area (or a high-efficiency driving area) of a compressor by considering the efficiency aspect, and executing an asymmetric operation in a high-load driving area (or a high freezing capacity driving area).