Compressor Speed Control During Defrosting to Protect Suction Pressure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
During defrosting operations in air conditioners, increasing the compressor's rotational speed to enhance defrosting efficiency can lead to reduced suction pressure, potentially damaging the compressor or triggering low-pressure protection controls, which prolongs the defrosting time and delays heating restoration.
Innovation Solution
The air conditioner is configured to drive the compressor at a predetermined rotational speed based on the total capacity of the flow rate adjustment valve and refrigerant pipe lengths during defrosting, preventing significant suction pressure reduction and ensuring the compressor operates within safe pressure limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compressor rotational speed is increased during defrosting operation, then the defrosting efficiency is improved, but the suction pressure is significantly reduced which may damage the compressor or trigger low-pressure protection controls
Solution Approach 1:
The patent applies dynamics by making the compressor rotational speed variable rather than fixed. The control unit adjusts the rotational speed based on real-time suction pressure feedback, allowing the system to optimize defrosting efficiency while preventing suction pressure from dropping below safe thresholds. This dynamic adjustment resolves the contradiction between high-speed defrosting and compressor protection.
Solution Approach 2:
The patent implements feedback control by continuously monitoring suction pressure during defrosting operation and using this information to adjust compressor speed. When suction pressure approaches critical levels, the control unit reduces rotational speed to maintain pressure above the lower limit, thereby preventing compressor damage while still achieving effective defrosting.
2Loss of time
If the compressor rotational speed is increased at the start of defrosting operation, then the defrosting operation time is shortened, but the suction pressure falls below the performance lower limit value due to pull-down effect
Solution Approach 1:
The patent applies preliminary action by starting the defrosting operation at a moderate compressor speed rather than immediately at high speed. This allows the system to establish stable suction pressure before increasing the rotational speed for intensive defrosting, thereby avoiding the pull-down effect that would otherwise cause pressure to fall below operational limits.
Solution Approach 2:
The patent uses periodic action by implementing staged compressor speed adjustment during defrosting. The control unit increases rotational speed in steps or intervals rather than all at once, allowing the refrigerant system to adapt and maintain pressure stability while progressively achieving effective defrosting over time.
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 configuration prevents compressor damage and premature low-pressure protection activation, allowing for efficient defrosting and timely restoration of heating operations by maintaining suitable suction pressure.
Implementation Method 1
a compressor (21), a flow passage switching unit (22), an outdoor heat exchanger (23)
Implementation Method 2
an outdoor heat exchanger (23)... heat exchange efficiency in the outdoor heat exchanger may be degraded
Implementation Method 3
a high-temperature refrigerant discharged from the compressor flows into the outdoor heat exchanger and melts frost formed on the outdoor heat exchanger
Data Source
AI summary
An outdoor unit control unit 200 has a defrosting operation condition table 300a that defines an activation rotational speed Cr in accordance with a total sum of flow rate coefficients Cva that is a total sum of flow rate coefficients Cv representing capacities of indoor expansion valves 52a to 52c. The outdoor unit control unit 200 calculates the total sum of the flow rate coefficients Cva by adding the flow rate coefficient Cv of each of the indoor expansion valves 52a to 52c, and refers to the defrosting operation condition table 300a, so as to determine the activation rotational speed Cr. Then, the outdoor unit control unit 200 activates a compressor 21 at the determined activation rotational speed Cr when starting a defrosting operation, maintains this activation rotational speed Cr for a predetermined time from the start of the defrosting operation, and drives the compressor 21.