Compressor Motor Liquid Cooling for Stator End Coils and Rotor
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Solution Overview
Problem
Existing electric motor assemblies, particularly those used in compressor air ends, face inefficiencies due to limited heat transfer capabilities, leading to higher operating temperatures and reduced performance, especially in regions like the stator end coils and rotor, which can result in motor inefficiency and magnet degradation.
Innovation Solution
A liquid cooling system is implemented where coolant is directly applied to the stator and rotor surfaces, enhancing heat transfer by eliminating the stator sleeve and epoxy encasement, and using spray cooling and direct contact with the stator end coils, while also circulating coolant through passages between the rotor and shaft to extract heat from the rotor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a stator sleeve and epoxy encasement are used to protect the stator, then structural strength and protection are improved, but heat transfer resistance increases and cooling efficiency deteriorates
Solution Approach 1:
The patent removes the stator sleeve and epoxy encasement that were previously used to protect the stator. By taking out these protective layers, the patent eliminates the heat transfer resistance they introduced, allowing direct liquid cooling contact with the stator surface. This resolves the contradiction by sacrificing the protective function (which can be achieved through alternative means) to improve heat transfer and reduce stator temperature.
Solution Approach 2:
The patent introduces liquid coolant as an intermediary medium to facilitate heat transfer from the stator. The coolant directly contacts the stator surface (or contacts it through a thin wall in some embodiments), serving as an efficient heat transfer mediator that overcomes the thermal resistance of traditional protective encasements, thereby reducing stator temperature while maintaining structural integrity.
2Device complexity
If traditional cooling methods are used, then device complexity is reduced, but heat transfer efficiency is insufficient leading to motor inefficiency
Solution Approach 1:
The patent employs liquid hydraulic cooling by circulating coolant through channels and spray nozzles directly onto the stator and rotor surfaces. This hydraulic cooling system significantly improves heat transfer efficiency compared to traditional air cooling or contactless methods, thereby improving motor efficiency. The liquid coolant effectively removes heat from critical areas, resolving the energy efficiency issue while maintaining acceptable system complexity.
3Device complexity
If the rotor is cooled through conventional means, then device complexity is minimized, but heat extraction from the rotor is insufficient causing magnet degradation
Solution Approach 1:
The patent extracts heat from the rotor by introducing coolant flow through passages in the rotor shaft and spray nozzles that directly contact the rotor surface. This active cooling approach effectively removes heat from the rotor and permanent magnets, preventing magnet degradation and improving reliability. The solution maintains minimal device complexity by using straightforward coolant circulation rather than complex cooling structures.
4Reliability
If oversized motors are used to compensate for poor cooling, then reliability is improved, but cost and device size increase
Solution Approach 1:
The patent changes the thermal management parameters of the motor by implementing efficient liquid cooling. This parameter change (improved heat transfer coefficient) allows the motor to operate reliably at a smaller size. The enhanced cooling efficiency compensates for the reduced motor mass, maintaining reliability while reducing weight and cost. The direct liquid cooling enables better thermal management in a compact design.
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 improved cooling system increases motor efficiency by reducing heat transfer resistance, allowing the motor to operate at lower temperatures, enhancing performance and reducing the need for oversized motors, thus lowering costs and improving compressor system efficiency.
Implementation Method 1
The heat is removed from the motor by both conduction and convection: first by conduction through a series of elements (e.g., a stator stack, an interference contact region and a jacket wall, etc.)
Implementation Method 2
The heat is removed from the motor by both conduction and convection: first by conduction through a series of elements (e.g., a stator stack, an interference contact region and a jacket wall, etc.), and then by convection into the fluid flowing around the jacket
Implementation Method 3
spray cooling and direct contact with the stator end coils
Data Source
AI summary
A motor assembly cooling system includes a plurality of liquid passages inside a motor housing. The motor assembly is cooled by circulating a liquid directly over the outside surface of the stator stack, spraying liquid onto the stator end coil surfaces and/or circulating liquid in an interior space between the motor rotor and the mating rotor shaft. Waste heat from the motor stator and rotor is extracted allowing for a higher motor efficiency and/or a smaller motor size, resulting in a lower motor cost. The liquid may be a lubricant (e.g., oil) used to lubricate the bearing system in the air end and motor, or a coolant.