Multi-capacity compressor with variable speed drive and method of use
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Solution Overview
Problem
Multi-capacity compressors, such as two-capacity HVAC systems, cannot operate at a low enough capacity to match cooling loads during mild conditions, leading to inefficient operation, frequent cycling, and greater temperature variations, as they typically operate at 66% capacity rather than the lower speeds achieved by variable speed systems.
Innovation Solution
A multi-capacity compressor system that includes a variable-voltage variable-frequency drive, allowing the compressor to operate at high, medium, and low capacity settings by selectively coupling an AC line voltage source or the variable-voltage variable-frequency drive, with a processor controlling the capacity and speed to match the cooling load, and bypassing the variable-voltage variable-frequency drive for high and medium capacity settings to reduce operating losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a two-capacity compressor is used to provide high and low compression levels, then the system operates more efficiently at lower capacity with longer running periods and less noise, but the compressor cannot operate at a low enough capacity to match cooling loads during mild conditions
Solution Approach 1:
The compressor capacity control is segmented into multiple discrete levels (high, medium, low) using separate capacitors and control circuits. This allows the compressor to operate at distinct capacity levels rather than continuous variation, providing better adaptability to different cooling loads while maintaining efficient operation at each level.
Solution Approach 2:
The system dynamically switches between different capacity levels based on cooling load requirements. The control circuit continuously monitors system conditions and adjusts compressor capacity in real-time by switching between different capacitor configurations, enabling the compressor to adapt to varying load conditions while operating efficiently at each level.
2Use of energy by moving object
If a two-capacity compressor operates at 66% capacity on the low-capacity setting, then the system provides improved SEER, but frequent cycling and greater temperature variations occur
Solution Approach 1:
By segmenting the capacity control into multiple discrete levels including a medium capacity setting, the system prevents the compressor from operating at the inefficient 66% level. The segmented control allows the compressor to switch to either high or medium capacity settings, eliminating the problematic intermediate operating point that causes frequent cycling and temperature variations.
Solution Approach 2:
The control circuit incorporates feedback mechanisms that monitor system performance and automatically adjust compressor capacity to maintain optimal operation. When the system detects conditions that would lead to frequent cycling or temperature variations, the feedback control adjusts the capacity level to maintain stable operation and improve reliability.
3Adaptability or versatility
If a variable speed drive is added to enable continuous speed adjustment, then the compressor can match cooling loads more precisely, but the system complexity increases
Solution Approach 1:
Instead of implementing a continuous variable speed drive, the system segments the speed control into multiple discrete levels using separate capacitors and control circuits. This segmented approach provides sufficient adaptability to match different cooling loads while avoiding the complexity of continuous speed adjustment mechanisms.
Solution Approach 2:
The patent replaces complex mechanical variable speed drive mechanisms with an electrical control system using capacitors and control circuits. This substitution maintains the ability to adjust compressor capacity while significantly reducing mechanical complexity and improving reliability through electrical rather than mechanical control.
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 enhances energy efficiency, improving the Seasonal Energy Efficiency Ratio (SEER) by up to 5 points, reduces fan speeds for efficient heat transfer, and extends compressor operation at low capacity for longer cycles, providing more comfortable and efficient cooling.
Implementation Method 1
a variable-voltage variable-frequency drive coupled to the multi-capacity compressor and configured to operate the multi-capacity compressor at a variable speed
Implementation Method 2
a multi-capacity compressor configured to operate selectively at a high-capacity setting, a medium-capacity setting, and a low-capacity setting to provide a compressor output
Implementation Method 3
providing more comfortable and efficient cooling
Data Source
AI summary
An HVAC system including a multi-capacity compressor, and a control system for the multi-capacity compressor are described herein. The control system includes an AC line voltage source, a variable-voltage variable-frequency drive, and a processor. The AC line voltage source is configured to operate the multi-capacity compressor. The variable-voltage variable-frequency drive is coupled to the AC line voltage source and is configured to operate the multi-capacity compressor at a variable speed. The processor is coupled to the AC line voltage source and the variable-voltage variable-frequency drive and is configured to selectively couple the AC line voltage source and the variable-voltage variable-frequency drive to the multi-capacity compressor to operate the multi-capacity compressor. The processor is further configured to transmit a capacity control signal to the multi-capacity compressor. The capacity control signal is instructive to operate the multi-capacity compressor in one of a plurality of capacity settings.