Compressor Frequency Control to Minimize Air Conditioner Thermo-Off Cycling
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Solution Overview
Problem
The reduction in compressor operating frequency leads to liquid back phenomena, oil viscosity issues, discomfort due to reduced dehumidification, and inefficient intermittent operation, causing reliability and comfort problems in air-conditioning systems.
Innovation Solution
An air-conditioning apparatus with a controller that performs thermo-off postponement control, temporarily reducing the compressor operating frequency to a minimum level when the indoor temperature meets specific conditions, allowing continuous operation instead of immediate shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the compressor operating frequency is reduced to match the air conditioning load, then energy efficiency is improved, but liquid back phenomenon occurs and compressor reliability deteriorates
Solution Approach 1:
The patent dynamically adjusts the compressor operating frequency based on operating conditions (outdoor temperature, load requirements). By changing the frequency parameter adaptively rather than operating at fixed low frequency, the system maintains reliability while improving energy efficiency. The controller modifies frequency within a safe range to prevent liquid back phenomenon.
Solution Approach 2:
The system uses feedback control by monitoring operating conditions and adjusting compressor frequency accordingly. The controller continuously evaluates the operating state and modifies frequency to prevent harmful conditions while optimizing efficiency, creating a closed-loop control system that balances reliability and energy consumption.
2Loss of energy
If the compressor operating frequency is reduced to match the air conditioning load, then energy efficiency is improved, but oil return deteriorates due to increased oil viscosity
Solution Approach 1:
The patent adjusts compressor operating frequency as a variable parameter based on outdoor temperature and load conditions. By preventing operation at excessively low frequencies where oil viscosity increases, the system maintains proper oil return while achieving energy efficiency improvements in the optimal frequency range.
3Loss of energy
If the compressor operating frequency is reduced to match the air conditioning load, then energy efficiency is improved, but dehumidification amount decreases causing comfort deterioration
Solution Approach 1:
The system dynamically adjusts compressor frequency to optimize both energy efficiency and dehumidification performance. By maintaining frequency above critical thresholds, the patent ensures sufficient dehumidification capability while avoiding unnecessary high-frequency operation, thus balancing comfort and energy consumption.
4Reliability
If the lowest operating frequency is increased through up correction to prevent liquid back and maintain comfort, then reliability and comfort are improved, but air conditioning capacity cannot be reduced sufficiently
Solution Approach 1:
The patent implements dynamic frequency adjustment where the lowest operating frequency is not fixed but adapts based on outdoor temperature and operating conditions. This dynamic approach allows the system to maintain reliability and comfort when needed while reducing capacity when conditions permit, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The system changes the operating frequency parameter dynamically rather than using a fixed corrected minimum frequency. By adjusting frequency based on real-time conditions, the patent achieves both reliability maintenance and capacity flexibility, allowing sufficient capacity reduction when operating conditions allow.
5Productivity
If intermittent operation is performed to reduce air conditioning capacity when load decreases, then equipment efficiency decreases and indoor temperature varies significantly, but capacity reduction is achieved
Solution Approach 1:
The patent uses dynamic frequency modulation to continuously adjust capacity rather than using intermittent on-off operation. This dynamic control maintains steady operation that preserves equipment efficiency while achieving the desired capacity reduction, eliminating the temperature variations and efficiency losses associated with intermittent operation.
Solution Approach 2:
The system maintains continuous compressor operation at optimized frequency rather than interrupting operation. This continuity ensures stable indoor temperature and maintains equipment efficiency while still achieving capacity reduction through frequency control, preventing the harmful effects of intermittent operation.
Data Source
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AI summary
[Object] An air-conditioning apparatus that can minimize an intermittent operation of the compressor so that a decrease in efficiency of the air-conditioning apparatus caused by the intermittent operation and a variation of an indoor inlet temperature caused by the intermittent operation can be reduced. [Solution] It is determined whether thermo-off postponement control is allowed or not on the basis of a current compressor operating frequency when a thermo-off condition is satisfied. If it is determined that thermo-off postponement control is allowed, the thermo-off postponement control in which a lowest operating frequency in an operating frequency range of a compressor 1 is temporarily reduced within a range greater than or equal to a minimum operating frequency of the compressor 1 in use so as to continue an operation. If it is determined that thermo-off postponement control is not allowed, thermo-off of stopping the compressor 1 is performed.