Linear Compressor Drive Circuit With Totem-Pole Voltage Modulation
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Solution Overview
Problem
Linear compressors in refrigeration appliances face inefficiencies due to complex and costly single-phase variable-frequency drive systems with high switching losses, which require a more efficient power delivery mechanism.
Innovation Solution
A variable capacity drive circuit utilizing a totem pole configuration of four-quadrant switches and a controller to modulate the excitation voltage applied to the motor, transitioning between states defined by positive and negative firing angles at a frequency determined by the AC line voltage to control voltage application during positive and negative half-cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single-phase variable-frequency drive with H-bridge inverter and front-end rectifier is used to control the linear compressor, then the motor speed and force can be controlled, but the system becomes complex and costly with high switching losses
Solution Approach 1:
The patent extracts and eliminates the complex H-bridge inverter and front-end rectifier from the drive system. Instead of using a full-bridge configuration, the invention employs a simplified single-switch topology that directly controls the compressor motor, removing unnecessary circuitry while maintaining speed and force control capabilities
Solution Approach 2:
The patent inverts the conventional approach by using a single switch with anti-parallel diodes instead of four switches in an H-bridge configuration. This inversion of the circuit topology achieves the same control function with significantly reduced complexity and switching losses
2Ease of operation
If a single-phase variable-frequency drive with H-bridge inverter is used, then motor control is achieved, but switching losses increase
Solution Approach 1:
The patent removes the multiple switching devices from the circuit, extracting only the essential single switch and anti-parallel diodes needed for control. This elimination of redundant switches directly reduces switching losses while maintaining motor control functionality
Solution Approach 2:
The patent employs a minimal switch configuration that reduces the number of active switching components, thereby reducing cumulative switching losses. The anti-parallel diodes provide passive current paths that eliminate the need for additional active switches, reducing energy loss
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 reduces energy losses and operational costs by efficiently controlling the voltage applied to the compressor, enhancing the performance and efficiency of the linear compressor.
Implementation Method 1
a driving coil that generates a force for moving the piston forward and backward within the housing
Data Source
AI summary
A method for operating a variable capacity drive circuit of a compressor includes operating first and second four-quadrant switches in a first state in which the first four-quadrant switch is closed and the second four-quadrant switch is open such that a voltage seen by the motor is equal to an AC line voltage. The method also includes operating the first and second four-quadrant switches in a second state where the first four-quadrant switch is open and the second four-quadrant switch is closed such that the voltage seen by the motor is to zero. Further, the method includes providing a positive firing angle and a negative firing angle for defining when the first and second four-quadrant switches are operated in each of the first and second states. Moreover, the method also includes transitioning between the first and second states using the firing angles at a switching frequency determined by the AC line voltage frequency.