High capacity chiller compressor
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Solution Overview
Problem
Existing large capacity centrifugal compressors face inefficiencies due to high shaft masses and diameters, power density issues, magnetic bearing controller failures, and complex maintenance requirements, limiting capacity and operational flexibility in refrigeration systems.
Innovation Solution
The design incorporates a permanent magnet motor with a smaller diameter rotor assembly, utilizing refrigerant gas for cooling, a modular construction for easier maintenance, and a variable frequency drive to enhance efficiency and capacity, allowing for independent cooling of motor and stator assemblies and reducing the number of compressors needed for high-capacity installations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If induction motors are used to drive large capacity compressors at high speeds, then power output is increased, but efficiency deteriorates due to excessive heat losses
Solution Approach 1:
The patent replaces the induction motor with a permanent magnet motor, substituting electromagnetic induction with direct magnetic field interaction. This eliminates the need for rotor bars and end rings, reducing electrical losses and heat generation while maintaining high power output capability at speeds exceeding 3600 RPM.
Solution Approach 2:
The patent changes the motor type parameter from induction to permanent magnet, which fundamentally alters the efficiency characteristics. The permanent magnet motor maintains high efficiency across a broader speed range, particularly at the high speeds required for refrigerants like R-134a, by eliminating resistive losses in the rotor.
2Loss of energy
If centrifugal compressors are used for large cooling capacities, then thermal efficiency is improved, but shaft mass and diameter increase causing power density issues
Solution Approach 1:
The patent replaces traditional lubricated bearings with magnetic bearings, eliminating mechanical contact and the associated shaft support structure. This reduces shaft mass and diameter while maintaining the high thermal efficiency of centrifugal compression, as magnetic bearings provide support without requiring heavy mechanical components.
Solution Approach 2:
The patent employs magnetic bearing technology that combines electromagnetic fields with mechanical support functions, creating a composite system that provides both bearing support and reduced mass. The magnetic field acts as a non-contact support mechanism, allowing for lighter shaft construction while maintaining structural integrity.
3Loss of energy
If magnetic bearings are used in high speed compressors, then efficiency is improved, but reliability deteriorates due to controller failures
Solution Approach 1:
The patent incorporates backup mechanical bearings positioned to receive the rotor in the event of magnetic bearing failure. This redundant support system provides a safety cushion, preventing catastrophic failure and allowing for controlled shutdown or continued operation in a degraded mode, thereby improving reliability while maintaining the efficiency benefits of magnetic bearings during normal operation.
4Ease of manufacture
If single stage compressors are used for comfort cooling, then cost is reduced, but capacity is limited
Solution Approach 1:
The patent designs a single stage centrifugal compressor with a permanent magnet motor that can operate efficiently across a wide capacity range, from comfort cooling to large capacity industrial applications. The high efficiency motor and magnetic bearing combination allows the same basic compressor design to serve multiple capacity requirements, eliminating the need for separate single-stage and multi-stage designs for different applications.
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 approach increases power output and efficiency, reduces maintenance needs, and achieves cooling capacities exceeding 800 standard refrigeration tons, addressing the limitations of existing systems by enhancing power density and operational flexibility.
Implementation Method 1
The motor includes a stator assembly having a plurality of magnetically conductive laminations stacked along a stator central axis to form a magnetically conductive stator core, and a rotor assembly including a permanent magnet mounted to a rotor central axis
Implementation Method 2
The motor is cooled by a cooling medium flowing through a motor cooling passage defined by the motor shaft
Implementation Method 3
The stator assembly is cooled by the cooling medium flowing through the stator assembly
Data Source
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AI summary
A high efficiency, low maintenance single stage or multi-stage centrifugal compressor assembly for large cooling installations. The assembly is highly efficient by virtue of a variable frequency drive (VFD) that drives a permanent magnet motor and matches compressor speed with compressor load, a direct drive impeller that eliminates gearing losses, and magnetic bearings that reduce frictional losses. The back-emf produced by the motor provides an intermediate power source for the magnetic bearings in the event of a loss of electrical power. A cooling system provides direct cooling of the rotor with gas refrigerant, and cooling of the stator with liquid refrigerant. Modular construction allows the compressor to be retrofit with upgrades. An inlet guide vane system operates without need for oil lubrication. The use of light metal castings and elimination of gearing reduces the weight to one-third or less of comparably powered conventional units.