Scroll compressor differential pressure control during compressor startup transitions
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Solution Overview
Problem
Existing cooling systems face issues with undirected unloading of scroll compressors due to low pressure differences, leading to reduced cooling capacity and temperature control instability, especially at varying ambient temperatures.
Innovation Solution
Implementing a method that dynamically adjusts compressor parameters and fan speeds using proportional integral derivative (PID) control and hysteresis-based adjustments to maintain pressure differences above a predetermined level, ensuring continuous operation and preventing compressor unloading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the pressure difference of the compressor is reduced to increase operating efficiency, then energy consumption is reduced, but the stationary scrolls separate from the orbiting scrolls causing undirected unloading and reducing cooling capacity
Solution Approach 1:
The patent implements dynamic capacity control of the compressor by adjusting the orbiting scroll's position along the stationary scroll using a variable frequency drive. This allows the compressor to operate at optimal pressure differences without causing undirected unloading, as the capacity is continuously adjusted to maintain stable operation. The dynamic adjustment prevents the stationary and orbiting scrolls from separating while optimizing energy consumption.
Solution Approach 2:
The control system continuously monitors the pressure difference across the compressor and adjusts the compressor capacity accordingly. When the pressure difference approaches the threshold for undirected unloading, the system reduces capacity to maintain stable operation. This feedback mechanism ensures the compressor operates efficiently without crossing into the unloading region, thereby maintaining both low energy consumption and adequate cooling capacity.
2Use of energy by moving object
If the compressor operates at minimal vapor displacement condition to reduce pressure difference, then energy consumption decreases, but the compressor becomes unloaded leading to reduced cooling capacity and temperature control stability
Solution Approach 1:
The variable capacity control mechanism dynamically adjusts the compressor operation to maintain minimal but stable vapor displacement. By continuously modulating the compressor capacity rather than operating at fixed minimal conditions, the system prevents undirected unloading while consuming minimal energy. This dynamic operation ensures temperature control stability is maintained even at low capacity settings.
Solution Approach 2:
The system changes the operating parameters of the compressor by adjusting the pressure difference and vapor displacement levels. By maintaining the pressure difference above the undirected unloading threshold through parameter adjustment, the compressor operates at minimal energy consumption while preserving temperature control stability. The parameter changes allow operation in a stable region just above the unloading boundary.
3Use of energy by moving object
If the compressor capacity is reduced to match low cooling demand, then energy efficiency improves, but the pressure difference drops causing undirected unloading
Solution Approach 1:
The dynamic capacity control system allows the compressor to operate at reduced capacity levels while maintaining stable operation. By continuously adjusting the orbiting scroll position, the system can reduce capacity to match low cooling demand without causing undirected unloading. The dynamic adjustment ensures the pressure difference remains above the instability threshold even at minimal capacity settings.
Solution Approach 2:
The control system uses feedback from pressure difference measurements to adjust compressor capacity in real-time. When capacity is reduced to match low demand, the feedback mechanism detects the approaching undirected unloading threshold and makes adjustments to maintain stable operation. This ensures energy efficiency is maximized while preventing operational instability.
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 approach effectively maintains compressor pressure ratios above the threshold for undirected unloading, enhancing cooling capacity and stability across different ambient conditions.
Implementation Method 1
controlling a condenser fan at a first speed according to a proportional integral derivative (PID) method
Implementation Method 2
hysteresis-based adjustments to maintain pressure differences above a predetermined level
Data Source
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AI summary
A method including: determining a cooling value; and comparing the cooling value to an activation point of a lead compressor. The lead compressor is in a tandem set of scroll compressors of a cooling system. The tandem set of compressors comprises a lag compressor. The method further includes: activating the lead compressor when the cooling value is greater than the activation point; activating the lag compressor subsequent to activating the lead compressor; and determining whether conditions exist including: an alarm associated with the lag compressor being generated, and the lead compressor being deactivated. The method further includes deactivating the lag compressor when at least one of the conditions exists in the cooling system.