Compressor Speed Control to Reduce Air Conditioner Thermo-Start/Stop
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Solution Overview
Problem
Existing air conditioning systems face challenges in reducing the frequency of compressor start/stop cycles (thermo-start/stop) while avoiding excess air conditioning capacity and associated increased power consumption or reduced efficiency.
Innovation Solution
Implementing a controller that adjusts the compressor's rotation speed based on request values from indoor units, prioritizing decrease in air conditioning capacity when indoor temperatures are within a threshold range of the target temperature, and switching to normal rotation speed control when temperatures deviate, to maintain efficient operation and reduce thermo-start/stop frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a time in which stopping of the compressor is prohibited is set to reduce the frequency of outdoor thermo-off, then the frequency of thermo-start/stop can be reduced, but the compressor might not be stopped even when the air conditioning capacity requested by each indoor unit decreases and the indoor temperature becomes a temperature not wanted for air conditioning operations, causing air conditioning operation in a state of excess air conditioning capacity to continue
Solution Approach 1:
The patent applies dynamics by making the compressor stop prohibition time variable rather than fixed. The control unit dynamically adjusts the prohibition time based on the aggregate request values from multiple indoor units, allowing the system to adapt to changing air conditioning demands and avoid both excessive start/stop cycles and prolonged excess capacity operation.
Solution Approach 2:
The patent implements feedback by continuously monitoring the aggregate request values from multiple indoor units and using this information to adjust the compressor stop prohibition time. This feedback mechanism ensures the compressor operation aligns with actual air conditioning needs, preventing both unnecessary stops and prolonged excess capacity operation.
2Use of energy by moving object
If the prohibiting time is set short to allow more frequent outdoor thermo-off, then it might be possible to stop the compressor when air conditioning capacity decreases, but it might not be possible to suppress the occurrence of outdoor thermo-off and sufficiently reduce the frequency of thermo-start/stop
Solution Approach 1:
The system dynamically adjusts the prohibition time based on real-time aggregate demand from indoor units, allowing flexible response to changing conditions rather than using a fixed short or long prohibition time.
Solution Approach 2:
The patent changes the parameter of prohibition time based on the aggregate request values from indoor units. When demand is high, the prohibition time is extended; when demand is low, it is shortened, optimizing both start/stop frequency and capacity efficiency.
3Power
If the rotation speed of the compressor is controlled on the basis of request values from indoor units requesting an increase in air conditioning capacity, then the air conditioning capacity can be increased to meet demand, but the frequency of outdoor thermo-off cannot be reduced when indoor temperatures are close to target temperatures
Solution Approach 1:
The control method dynamically switches between two control strategies based on temperature conditions: using request values for increasing capacity when temperatures are far from target, and using request values for decreasing capacity when temperatures are close to target, thereby optimizing both capacity response and start/stop frequency.
Solution Approach 2:
The system takes preliminary action by setting the prohibition time before outdoor thermo-off occurs, preventing the compressor from stopping when it would be beneficial to continue operation at reduced capacity, thus reducing thermo-start/stop frequency.
Data Source
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AI summary
A controller (8) of an air conditioning apparatus (1) performs a start/stop frequency-reducing rotation speed control in which the rotation speed of a compressor (21) is controlled on the basis of request values from indoor units requesting a decrease in air conditioning capacity, disregarding request values from indoor units requesting an increase in air conditioning capacity, when each indoor temperature at all indoor units (4a, 4b, 4c) performing air conditioning operation is within a scope of a prescribed threshold temperature range surrounding a target indoor temperature at each indoor unit (4a, 4b, 4c) performing air conditioning operation.