Variable Speed Compressor Using CVT Instead of VSDs
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Solution Overview
Problem
Existing variable speed compressor systems for air conditioning and refrigeration require expensive and complex variable speed drives (VSDs) to adjust compressor capacity, which are costly and inefficient, especially for large tonnage applications where VSDs for higher power levels are not commercially available.
Innovation Solution
A cooling system utilizing a continuous variable transmission (CVT) connected to a drive motor and a compressor, where a controller adjusts the output of the CVT based on the leaving chilled water temperature to vary the compressor speed, eliminating the need for a VSD and allowing for efficient power management without varying the drive motor speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable speed drives (VSDs) are used to adjust compressor capacity, then the system can vary cooling/heating capacity, but the system becomes expensive and complex
Solution Approach 1:
The patent extracts the speed variation function from the electrical domain (VSD) and relocates it to the mechanical domain (CVT). The CVT is inserted between the motor and compressor, allowing speed adjustment without modifying the electrical drive system. This separates the motor control function from the compressor speed control function, reducing overall system complexity.
Solution Approach 2:
The patent replaces the electrical control system (VSD) with a mechanical transmission system (CVT). Instead of using electrical frequency and voltage control to adjust motor speed, the system uses a continuous variable transmission mechanism to mechanically adjust the compressor speed while the motor operates at constant speed, thereby eliminating expensive electrical variable speed drive equipment.
2Adaptability or versatility
If VSDs are used for large tonnage applications, then capacity control is achieved, but VSDs for higher power levels are not commercially available
Solution Approach 1:
The patent substitutes mechanical transmission (CVT) for electrical drive control (VSD) in large tonnage applications where high-power VSDs are unavailable. The CVT mechanism can handle high torque and power levels mechanically, enabling capacity control in applications exceeding conventional VSD power ratings without requiring specialized electrical equipment.
3Use of energy by moving object
If constant speed motors are used with CVT, then motor efficiency is maintained, but the system requires a transmission mechanism
Solution Approach 1:
The patent introduces a CVT as an intermediary component between the constant-speed motor and the compressor. This intermediary mechanism allows the motor to operate at its optimal constant speed for maximum efficiency while the CVT handles the speed variation required for capacity control, effectively decoupling the motor operating conditions from the compressor speed requirements.
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
The CVT system reduces the need for costly gearboxes and VSDs, enabling efficient power management and capacity adjustment in refrigerant cycles, particularly suitable for large tonnage water chillers, by using hydrostatic, hydro-mechanical, or mechanical CVTs to optimize compressor performance and reduce size and power requirements.
Implementation Method 1
The CVT may be a hydrostatic or hydraulic, hydro-mechanical or mechanical (e.g., adjustable pulley) type CVT
Implementation Method 2
The CVT may be a hydrostatic or hydraulic, hydro-mechanical or mechanical (e.g., adjustable pulley) type CVT
Implementation Method 3
A compressor is used to compress a working fluid (i.e., the refrigerant) from initial (suction) conditions to compressed (discharge) conditions
Implementation Method 4
The controller increases the output of the CVT to the output drive shaft when the leaving chilled water temperature is above a set point
Implementation Method 5
The compressor is connected to an evaporator, which is connected to a condenser, which is connected to the compressor thereby forming a vapor-compression refrigerant cycle
Data Source
AI summary
A compressor, as well as a lightweight and strong casting for a compressor, are disclosed. The compressor, which may be a reciprocating compressor for use in compressing high-pressure refrigerants such as CO2, includes substantially reduced wall thicknesses (t) compared to prior art castings. The side walls of the compressor can be manufactured to such reduced thicknesses (t) through the use of a bridge spanning across the crankcase. This not only allows the opposing side walls to be manufactured of a thinner material, but the bottom cover removably mounted to the crankcase can be manufactured from a thinner and lighter material as well. Through the use of such a bridge, the resulting compressor is not only able to satisfy current strength requirements, but at significant weight, size and cost savings as well.