Rotary Compressor Motor Speed Control for Leakage Reduction
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Solution Overview
Problem
In rotary compressors, significant fluctuations in gas compression torque lead to rotational speed variations of the crankshaft during compression, resulting in increased refrigerant leakage from high-pressure to low-pressure chambers due to pressure differences, causing recompression losses.
Innovation Solution
A rotational speed control device that acquires the angle of rotation of the motor driving the crankshaft, determines when to adjust the motor speed based on predefined threshold values related to refrigerant leakage, pressure differences, and temperature or volume ratios between high-pressure and low-pressure chambers, using a sensorless vector control circuit to estimate and adjust the motor's rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the crankshaft rotational speed is allowed to fluctuate naturally during compression, then the motor operates smoothly without artificial speed control, but refrigerant leakage increases from high-pressure to low-pressure chamber due to extended compression time
Solution Approach 1:
The patent applies dynamics by making the motor rotational speed adjustable and variable during the compression cycle. The control device dynamically changes the motor speed based on the compression state, specifically increasing speed when the piston rotor is in the high-pressure chamber region to reduce refrigerant leakage time, and decreasing speed when in the low-pressure chamber region to maintain smooth operation.
Solution Approach 2:
The patent changes the operational parameters of the motor by adjusting its rotational speed according to the position of the piston rotor. The control device modifies the speed parameter in response to signals indicating whether the piston rotor is in the high-pressure or low-pressure chamber, thereby optimizing compression efficiency and reducing refrigerant leakage.
2Productivity
If the motor speed is increased to reduce refrigerant leakage time, then compression efficiency improves, but the motor consumes more energy and experiences higher mechanical stress
Solution Approach 1:
The patent implements periodic action by cyclically adjusting the motor speed according to the periodic motion of the piston rotor. The control device increases motor speed periodically when the piston rotor enters the high-pressure chamber region and decreases it when exiting, creating a rhythm that matches the compression cycle to minimize leakage while managing energy consumption.
Solution Approach 2:
The control device performs preliminary action by increasing the motor speed before and during the period when the piston rotor is in the high-pressure chamber region, where refrigerant leakage is most problematic. This proactive speed adjustment reduces leakage time before significant leakage can occur.
3Loss of energy
If the motor speed is continuously adjusted to minimize refrigerant leakage, then compression efficiency improves, but the control system complexity increases
Solution Approach 1:
The patent employs feedback control where the control device receives signals about the piston rotor position (indicating whether it is in the high-pressure or low-pressure chamber) and automatically adjusts the motor speed in response. This closed-loop feedback mechanism enables automatic optimization of compression efficiency without requiring complex manual control systems.
Data Source
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AI summary
A control device configured to prevent the leakage of a refrigerant gas in a low-pressure chamber from a high-pressure chamber in a rotary compressor is provided. A rotational speed control device acquires an angle of rotation of a motor used to rotatably drive a crankshaft for driving a piston rotor in the rotary compressor, compares a threshold value set in advance to correspond to an amount of leakage of the refrigerant gas from the high-pressure chamber to the low-pressure chamber in a cylinder with an angle of rotation of a crankshaft based on the acquired angle of rotation of the motor, determines whether to change a rotational speed of the motor, and changes a rotational speed command value to the motor when it is determined that the rotational speed is changed.