Three-Compressor Outdoor Unit Control for Oil Equalization
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Solution Overview
Problem
Existing outdoor units with multiple compressors face capacity shortfalls during high loads, as they inefficiently manage oil distribution and compressor operation, leading to inadequate indoor unit performance.
Innovation Solution
An outdoor unit with a controller that manages compressor startup and shutdown to maintain proper oil levels by operating one compressor at a low load while others operate normally, ensuring even oil distribution and preventing capacity shortfalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compressors are stopped one at a time during oil equalization mode, then oil distribution is maintained, but indoor unit capacity is insufficient at high load
Solution Approach 1:
The system segments the compressor operation into distinct phases: oil equalization phase (where compressors are stopped sequentially) and capacity provision phase (where compressors operate to meet demand). This segmentation allows the system to balance between oil distribution stability and capacity requirements by choosing appropriate operational modes based on system state
Solution Approach 2:
The control system dynamically adjusts compressor operation based on real-time conditions including load demand and oil level status. The system transitions between different operational states (oil equalization mode vs. normal operation mode) to optimize both oil distribution and capacity provision according to current system requirements
2Productivity
If compressors operate at full capacity during high load, then indoor unit capacity is sufficient, but oil distribution becomes uneven
Solution Approach 1:
The system implements periodic oil equalization cycles during operation. Between these periodic maintenance phases, compressors operate at full capacity to meet demand. The periodic intervention of oil equalization mode prevents cumulative oil distribution issues while maintaining high productivity during normal operation intervals
3Reliability
If oil equalization is performed by stopping compressors sequentially, then oil level is maintained, but system response time increases
Solution Approach 1:
The control system monitors oil levels and load conditions continuously, performing oil equalization proactively before oil distribution becomes critically uneven. By initiating oil equalization mode based on predictive criteria (oil level thresholds, operational duration), the system prevents severe imbalances without requiring extended shutdown periods, thus reducing time loss while maintaining reliability
Data Source
Figure 1
Figure 2A~2C
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AI summary
A capacity shortfall in an indoor unit at a high load is prevented. An outdoor unit (10) includes at least three compressors (CM1, CM2, CM3) and has an oil equalization mode function for maintaining a proper oil level in each of the compressors (CM1, CM2, CM3). The outdoor unit (10) includes a controller (12) that controls starting and stopping of the compressors (CM1, CM2, CM3) in the oil equalization mode such that one of the compressors (CM1, CM2, CM3) at a time is stopped or operated at a low load while the other compressors (CM1, CM2, CM3) are operated.